document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=979465>Question 979465</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a man is four times as old as his  son,in four years time,he will be three times as old. what are their ages? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #600732 by </B><A HREF=/tutors/aboutme.mpl?userid=ikleyn><B>ikleyn(52847)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ikleyn><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=ikleyn><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=600732\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> \r<BR>\n" );
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document.write( "Let &nbsp;<B>x</B>&nbsp; be the man's age now, &nbsp;and let &nbsp;<B>y</B>&nbsp; be the son's age now.\r<BR>\n" );
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document.write( "Then we have an equation \r<BR>\n" );
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document.write( "x = 4y,\r<BR>\n" );
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document.write( "according to the condition. \r<BR>\n" );
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document.write( "In &nbsp;4&nbsp; years the man's age will be &nbsp;x+4, &nbsp;and his son's age will be &nbsp;y+4.\r<BR>\n" );
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document.write( "Thus we have the second equation\r<BR>\n" );
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document.write( "x + 4 = 3*(y+4),\r<BR>\n" );
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document.write( "according to the condition. \r<BR>\n" );
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document.write( "So, &nbsp;we need to solve this system of linear equations\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=system%28x+=+4y%2C%0D%0Ax%2B4+=+3%2A%28y%2B4%29%29 ALIGN=MIDDLE  ALT=\"system%28x+=+4y%2C%0D%0Ax%2B4+=+3%2A%28y%2B4%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.\r<BR>\n" );
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document.write( "To solve it, &nbsp;substitute &nbsp;<B>x</B>&nbsp; from the first equation to the second one. &nbsp;You will have\r<BR>\n" );
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document.write( "4y + 4 = 3*(y+4),\r<BR>\n" );
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document.write( "4y + 4 = 3y + 12,\r<BR>\n" );
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document.write( "y = 12 - 4,\r<BR>\n" );
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document.write( "y = 8.\r<BR>\n" );
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document.write( "Thus the son age is &nbsp;8&nbsp; years now.<BR>\n" );
document.write( "Then the man's age is &nbsp;8*4 = 32&nbsp; years now. \r<BR>\n" );
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document.write( "The problem is solved.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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