document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=770096>Question 770096</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The age of Jack and John is 49. Jack is twice as old, as John was when Jack was as old as John is now. How old are the brothers? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #469283 by </B><A HREF=/tutors/aboutme.mpl?userid=josmiceli><B>josmiceli(19441)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josmiceli><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=josmiceli><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=469283\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+ ALIGN=MIDDLE  ALT=\"+a+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = Jack's age<BR>\n" );
document.write( "Let <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+ ALIGN=MIDDLE  ALT=\"+b+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = John's age<BR>\n" );
document.write( "--------------------<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+%2B+b+=+49+ ALIGN=MIDDLE  ALT=\"+a+%2B+b+=+49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "--------------<BR>\n" );
document.write( "The difference in their ages always<BR>\n" );
document.write( "stays the same, <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+-+b+ ALIGN=MIDDLE  ALT=\"+a+-+b+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "--------------<BR>\n" );
document.write( "Starting at the end of the problem,<BR>\n" );
document.write( "\" when Jack was as old as John is now \"<BR>\n" );
document.write( "So Jack's age was <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+ ALIGN=MIDDLE  ALT=\"+b+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "John had to have been <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+-+%28+a+-+b+%29+=+2b+-+a+ ALIGN=MIDDLE  ALT=\"+b+-+%28+a+-+b+%29+=+2b+-+a+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "at that time<BR>\n" );
document.write( "---------------<BR>\n" );
document.write( "It says that Jack is now twice that age, so<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+=+2%2A%28+2b+-+a+%29+ ALIGN=MIDDLE  ALT=\"+a+=+2%2A%28+2b+-+a+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+=+4b+-+2a+ ALIGN=MIDDLE  ALT=\"+a+=+4b+-+2a+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+3a+=+4b+ ALIGN=MIDDLE  ALT=\"+3a+=+4b+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+=+%28+3%2F4+%29%2Aa+ ALIGN=MIDDLE  ALT=\"+b+=+%28+3%2F4+%29%2Aa+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "----------------<BR>\n" );
document.write( "By substitution:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+%2B+b+=+49+ ALIGN=MIDDLE  ALT=\"+a+%2B+b+=+49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+%2B+%283%2F4%29%2Aa+=+49+ ALIGN=MIDDLE  ALT=\"+a+%2B+%283%2F4%29%2Aa+=+49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+%287%2F4%29%2Aa+=+49+ ALIGN=MIDDLE  ALT=\"+%287%2F4%29%2Aa+=+49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+=+%284%2F7%29%2A49+ ALIGN=MIDDLE  ALT=\"+a+=+%284%2F7%29%2A49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+=+28+ ALIGN=MIDDLE  ALT=\"+a+=+28+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+a+%2B+b+=+49+ ALIGN=MIDDLE  ALT=\"+a+%2B+b+=+49+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+b+=+21+ ALIGN=MIDDLE  ALT=\"+b+=+21+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Jack is 28 and John is 21<BR>\n" );
document.write( "-----------<BR>\n" );
document.write( "check:<BR>\n" );
document.write( "\" when Jack was as old as John is now \"<BR>\n" );
document.write( "Jack was 21<BR>\n" );
document.write( "John had to have been 7 years younger,<BR>\n" );
document.write( "or 14<BR>\n" );
document.write( "Jack's age now is twice that age, or 28<BR>\n" );
document.write( "OK<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );