document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=530681>Question 530681</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Two years ago, my age was 4 times that of my son. Eight years ago, my age was 10 times that of my son. Find age of my son now. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #350191 by </B><A HREF=/tutors/aboutme.mpl?userid=oberobic><B>oberobic(2304)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=oberobic><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=350191\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x = father's current age<BR>\n" );
document.write( "y = son's current age<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Two years ago...<BR>\n" );
document.write( "x-2<BR>\n" );
document.write( "y-2<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Father's age was 4 times son's age:<BR>\n" );
document.write( "(x-2) = 4(y-2)<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Eight years ago...<BR>\n" );
document.write( "x-8<BR>\n" );
document.write( "y-8<BR>\n" );
document.write( "Father's age was 10 times son's age:<BR>\n" );
document.write( "(x-8) = 10(y-8)<BR>\n" );
document.write( ".<BR>\n" );
document.write( "So, we have two equations and two unknowns.<BR>\n" );
document.write( "That suggests a system of linear equations can be used to solve them.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "x-2 = 4y -8<BR>\n" );
document.write( "x -4y = -6<BR>\n" );
document.write( ".<BR>\n" );
document.write( "x-8 = 10y -80<BR>\n" );
document.write( "x -10y = -72<BR>\n" );
document.write( ".<BR>\n" );
document.write( "x -4y = -6<BR>\n" );
document.write( "x -10y = -72<BR>\n" );
document.write( "------------- subtract<BR>\n" );
document.write( "6y = 66<BR>\n" );
document.write( "divide both sides by 6<BR>\n" );
document.write( "y = 11<BR>\n" );
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document.write( "So, the son is now 11 years old.<BR>\n" );
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document.write( "To check this answer...<BR>\n" );
document.write( "substitute y=11 to find x<BR>\n" );
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document.write( "(x-2) = 4(11-2)<BR>\n" );
document.write( "x -2 = 44 - 8<BR>\n" );
document.write( "x = 38<BR>\n" );
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document.write( "check these values using the third equation<BR>\n" );
document.write( ".<BR>\n" );
document.write( "x-8 = 10(y-8)<BR>\n" );
document.write( "x-8 = 30<BR>\n" );
document.write( "y-8 = 3<BR>\n" );
document.write( "10*3 = 30<BR>\n" );
document.write( "Correct.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Answer:  The son is now 11 years old.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );