document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1059463>Question 1059463</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The sum of the ages of Mark's two sons is equal to his own age of 51. <BR>\n" );
document.write( "21 years ago, Mark's older son was twice as old as the younger son. <BR>\n" );
document.write( "How old was Mark when the sum of his sons' ages was half his age? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #674546 by </B><A HREF=/tutors/aboutme.mpl?userid=addingup><B>addingup(3677)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=addingup><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=addingup><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=674546\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a+b = 51 so a = 51-b<BR>\n" );
document.write( "a-21 = 2(b-21)<BR>\n" );
document.write( "a-21 = 2b-21 substitute for a:<BR>\n" );
document.write( "51-b-21 = 2b-21<BR>\n" );
document.write( "72 = 3b flip it<BR>\n" );
document.write( "3b = 72<BR>\n" );
document.write( "b = 24 and a = 51-b = 51-24 = 27<BR>\n" );
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document.write( "check: 21 years ago:<BR>\n" );
document.write( "a = 27-21 = 6<BR>\n" );
document.write( "b = 24-21 = 3 and 3 is 1/2 of 6 Correct answer.<BR>\n" );
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document.write( "Mark is 51 and 51/2= 25.5. The boys are 3 years apart, as I just showed. Let's call the age of the youngest x, and the oldest will be x+3. So:<BR>\n" );
document.write( "x+x+3 = 25.5<BR>\n" );
document.write( "2x = 22.5<BR>\n" );
document.write( "x = 11.25 the youngest was 11 1/4 years old.<BR>\n" );
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document.write( "The youngest is now 24 and 24-11 1/4 = 12 3/4<BR>\n" );
document.write( "Mark is now 51 and 51-12 3/4 = 38 1/4 This is how old Mark was, 38.25 or 38 1/4<BR>\n" );
document.write( ":<BR>\n" );
document.write( "John </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );