document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=120849>Question 120849</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In five years time a father will be three times as old as his son. Five years ago, the father was six times as old as his son. Find their present age. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #88639 by </B><A HREF=/tutors/aboutme.mpl?userid=ptaylor><B>ptaylor(2198)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ptaylor><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=ptaylor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=88639\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "Let x=son's present age; x+5=son's age in five year's time; x-5=son's age five year's ago<BR>\n" );
document.write( "And let y=father's present age; y-5= father's age five years ago and y+5=father's age in five year's time\r<BR>\n" );
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document.write( "Now we are told that:\r<BR>\n" );
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document.write( "y+5=3(x+5) get rid of parens<BR>\n" );
document.write( "y+5=3x+15 subtract 5 from both sides<BR>\n" );
document.write( "y+5-5=3x+15-5 collect like terms<BR>\n" );
document.write( "y=3x+10-----------------------------------------eq1<BR>\n" );
document.write( "and that:<BR>\n" );
document.write( "y-5=6(x-5) get rid of parens<BR>\n" );
document.write( "y-5=6x-30  add 5 to both sides<BR>\n" );
document.write( "y-5+5=6x-30+5  collect like terms\r<BR>\n" );
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document.write( "y=6x-25------------------------------eq2\r<BR>\n" );
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document.write( "Substitute y=3x+10 from eq1 into eq2:\r<BR>\n" );
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document.write( "3x+10=6x-25 subtract 3x from and add 25 to both sides\r<BR>\n" );
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document.write( "3x-3x+10+25=6x-3x-25+25  collect like terms\r<BR>\n" );
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document.write( "35=3x divide both sides by 3<BR>\n" );
document.write( "x=11 2/3 years-----------------present age of son<BR>\n" );
document.write( "substitute 11 2/3 for x into eq1:\r<BR>\n" );
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document.write( "y=3*(11 2/3)+10<BR>\n" );
document.write( "y=35+10=45 years---------------------present age of father<BR>\n" );
document.write( "CK<BR>\n" );
document.write( "y+5=3(x+5)<BR>\n" );
document.write( "45+5=3*(11 2/3)+15<BR>\n" );
document.write( "50=50<BR>\n" );
document.write( "and<BR>\n" );
document.write( "y-5=6(x-5)<BR>\n" );
document.write( "45-5=6*(11 2/3)-30<BR>\n" );
document.write( "40=70-30<BR>\n" );
document.write( "40=40\r<BR>\n" );
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document.write( "Hope this helps---ptaylor </SPAN>\n" );
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