For example, I have an xml file that contains information the coefficient of rank PT 2. Using XSL to read the data in xml PT.

<?xml version = "1.0"?>
<?xml-stylesheet type="text/xsl" href="ptb2.xsl"?>
<PTB2>
	<HeSo giatri = "1"/>
	<HeSo giatri = "3"/>
	<HeSo giatri = "2"/>
</PTB2>

<?xml version = "1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:math="http://exslt.org/math"
                version="1.0">

	<xsl:template match="/">
		<xsl:variable name = "a" select="PTB2/HeSo[1]/@giatri"/>
		<xsl:variable name = "b" select="PTB2/HeSo[2]/@giatri"/>
		<xsl:variable name = "c" select="PTB2/HeSo[3]/@giatri"/>
		
		<xsl:variable name = "delta" select="$b * $b - 4 * $a * $c"/>
		<xsl:if test = "$delta &lt; 0">
			PT Vo nghiem
		</xsl:if>
		
		<xsl:if test = "$delta = 0">
			PT Co nghiem kep x = 
			<xsl:value-of select = "-$b div 2 div $a"/>
		</xsl:if>
		
		
		<xsl:if test = "$delta &gt; 0">
			PT Co 2 nghiem phan biet <br/>
			x1 = 
			<xsl:value-of select = "(-$b + math:sqrt($delta)) div 2 div $a"/>
			<br/>
			x2 = 
			<xsl:value-of select = "(-$b - math:sqrt($delta)) div 2 div $a"/>
		</xsl:if>
		
	</xsl:template>
</xsl:stylesheet>