document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=38374>Question 38374</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Bob's father is 3 times old as Bob. 4 years ago, he was 4 times older. How old is Bob? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #23859 by </B><A HREF=/tutors/aboutme.mpl?userid=fractalier><B>fractalier(6550)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=fractalier><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=fractalier><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=23859\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Always assign variables in age problems in the NOW.<BR>\n" );
document.write( "Let B be Bob's age NOW.<BR>\n" );
document.write( "Let F be the father's age NOW.<BR>\n" );
document.write( "From the problem,<BR>\n" );
document.write( "F = 3B<BR>\n" );
document.write( "F - 4 = 4(B - 4)<BR>\n" );
document.write( "Substituting, we get<BR>\n" );
document.write( "3B - 4 = 4B - 16<BR>\n" );
document.write( "-B = -12<BR>\n" );
document.write( "and<BR>\n" );
document.write( "B = 12  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );