Question 1195117
bob is younger than bill.
<pre>
                           bob:  when I am your age      bill: when I was your age

BILL          x+d             x+2d=36                     x

BOB          x                 x+d                        x-d=3
</pre>
{{{system(x+2d=36,x-d=3)}}}


{{{system(x+2d=36,2x-2d=6)}}}


{{{ADD}}}:
{{{3x=39}}}

{{{highlight(x=13)}}}

-

{{{x-d=3}}}
{{{x-3=d}}}
{{{13-3=d}}}
{{{d=10}}}

-

BILL, {{{x+d=13+10=highlight(23)}}}