<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0021 - Disclosure - 3. INVENTORIES (Tables)</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>From2012-12-01to2013-05-31</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001436549</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2012-12-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-05-31T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="May 31, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_InventoryDisclosureAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Inventory Disclosure [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_ScheduleOfInventoryCurrentTableTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2012-12-01to2013-05-31" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 45pt"&gt;Inventories consisted of the following:&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;table cellspacing="0" cellpadding="0" style="font: 8pt Calibri, Helvetica, Sans-Serif; width: 100%"&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1pt solid"&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;As at&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;November 30,&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;2012&lt;/b&gt;&lt;/p&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="border-bottom: black 1pt solid"&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;As at&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;May 31,&lt;/b&gt;&lt;/p&gt;
        &lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: center"&gt;&lt;b&gt;2013&lt;/b&gt;&lt;/p&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="width: 78%; text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Raw materials&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 9%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;330,627&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 9%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&amp;#160;624,444&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Finished goods&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;739,205&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;&amp;#160;348,215&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="text-indent: 0pt; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;Equipment (i)&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;126,966&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;126,966&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: white"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td colspan="2" style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="text-align: right; line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="vertical-align: bottom; background-color: #CCEEFF"&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;1,196,798&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.25pt double; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;1,099,625&lt;/font&gt;&lt;/td&gt;
    &lt;td style="line-height: 115%"&gt;&amp;#160;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;
&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;table cellspacing="0" cellpadding="0" style="font: 8pt Calibri, Helvetica, Sans-Serif; width: 100%"&gt;
&lt;tr style="vertical-align: top"&gt;
    &lt;td style="width: 4%; text-align: right; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;(i)&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 96%; line-height: 115%"&gt;&lt;font style="font: 8pt Times New Roman, Times, Serif"&gt;During fiscal 2012, certain oil processing research and development related equipment previously sold in fiscal 2011 was returned.&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;
&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher SEC

 -Name Regulation S-X (SX)

 -Number 210

 -Section 2

 -Paragraph 6

 -Subparagraph a,b,c

 -Article 5



</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Schedule of Inventories</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>3. INVENTORIES (Tables)</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://methes.com/role/InventoriesTables</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
