document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=990631>Question 990631</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The sum of present ages of A and B is 7 times the difference of their ages. 5 years hence, their total ages will be 9 times the difference of their ages. What is the present age of elder one (in years)? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #610671 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=610671\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The sum of present ages of A and B is 7 times the difference of their ages.<BR>\n" );
document.write( " 5 years hence, their total ages will be 9 times the difference of their ages.<BR>\n" );
document.write( " What is the present age of elder one (in years)?<BR>\n" );
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document.write( "let a = A's present age<BR>\n" );
document.write( "let b = B's age<BR>\n" );
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document.write( "Write an equation for each statement<BR>\n" );
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document.write( "\"The sum of present ages of A and B is 7 times the difference of their ages.\" <BR>\n" );
document.write( "a + b = 7(a-b)<BR>\n" );
document.write( "a + b = 7a - 7b<BR>\n" );
document.write( "b + 7b = 7a - a<BR>\n" );
document.write( "8b = 6a<BR>\n" );
document.write( "b = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=6%2F8 ALIGN=MIDDLE  ALT=\"6%2F8\"   DISABLED_style= \"max-width:90%; height:auto;\" >a<BR>\n" );
document.write( "b = .75a<BR>\n" );
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document.write( "\"5 years hence, their total ages will be 9 times the difference of their ages.\"<BR>\n" );
document.write( "(their difference in their ages will never change)<BR>\n" );
document.write( "a+5 + b+5 = 9(a - b) <BR>\n" );
document.write( "a + b + 10 = 9a - 9b<BR>\n" );
document.write( "b + 9b + 10 = 9a - a<BR>\n" );
document.write( "10b + 10 = 8a<BR>\n" );
document.write( "Replace b with .75a, from the 1st statement<BR>\n" );
document.write( "10(.75a) + 10 = 8a<BR>\n" );
document.write( "7.5a + 10 = 8a<BR>\n" );
document.write( "10 = 8a - 7.5a<BR>\n" );
document.write( "10 = .5a<BR>\n" );
document.write( "a = 10/.5<BR>\n" );
document.write( "a = 20 yrs old and he is the eldest<BR>\n" );
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document.write( "To check this find b's age<BR>\n" );
document.write( "b = .75(20)<BR>\n" );
document.write( "b = 15 yrs, 5 yrs younger than a<BR>\n" );
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document.write( "Check this in the 2nd statement<BR>\n" );
document.write( "\"5 years hence, their total ages will be 9 times the difference of their ages.\" <BR>\n" );
document.write( "20+5 + 15+5 = 9(5)<BR>\n" );
document.write( "25 + 20 = 45 </SPAN>\n" );
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