document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=242951>Question 242951</A>: <I><SPAN STYLE=\"word-break: break-all;\"> in four years time, a father will be three times as old as his son. six years ago he was seven times as old as his son. how old are they now ? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #178123 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=178123\">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( "In 4 years, x will be 3 times y, which is shown as: x+4 = 3(y+4)<BR>\n" );
document.write( "Six years ago (x-6) he was 7 times as old: x-6 = 7(y-6)<BR>\n" );
document.write( "...<BR>\n" );
document.write( "Summarizing what we know:<BR>\n" );
document.write( "x + 4 = 3(y+4) = 3y + 12<BR>\n" );
document.write( "x - 6 = 7(y-6) = 7y - 42<BR>\n" );
document.write( "...<BR>\n" );
document.write( "Deriving a value for x:<BR>\n" );
document.write( "x + 4 = 3y + 12<BR>\n" );
document.write( "x = 3y + 12 - 4 <BR>\n" );
document.write( "x = 3y + 8<BR>\n" );
document.write( "...<BR>\n" );
document.write( "Substituting into the second equation,<BR>\n" );
document.write( "x - 6 = 7y - 42<BR>\n" );
document.write( "3y+8 -6 = 7y -42<BR>\n" );
document.write( "3y+2 = 7y - 42<BR>\n" );
document.write( "2+42 = 7y-3y<BR>\n" );
document.write( "44 = 4y<BR>\n" );
document.write( "4y = 44<BR>\n" );
document.write( "y = 11<BR>\n" );
document.write( "...<BR>\n" );
document.write( "Going back to a formula we know<BR>\n" );
document.write( "x = 3y + 8<BR>\n" );
document.write( "x = 3(11) + 8 = 41<BR>\n" );
document.write( "x = 41<BR>\n" );
document.write( "...<BR>\n" );
document.write( "Check our work by checking the other facts given.<BR>\n" );
document.write( "How old will they be in 4 years?<BR>\n" );
document.write( "x+4 = 41+4 = 45<BR>\n" );
document.write( "y+4 = 11+4 = 15<BR>\n" );
document.write( "Does 15 = 3*15?  Yes, it does.<BR>\n" );
document.write( "How old were they 6 years ago?<BR>\n" );
document.write( "x-6 = 41-6 = 35<BR>\n" );
document.write( "y-6 = 11-6 = 5<BR>\n" );
document.write( "Is x = 7 times the son's age?<BR>\n" );
document.write( "35 = 7*5?  Yes.<BR>\n" );
document.write( "...<BR>\n" );
document.write( "So, we are confident the current ages are:<BR>\n" );
document.write( "father = 41<BR>\n" );
document.write( "son = 11 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );