Question 818557
Let a = altitude.
Let b = base.


{{{a=b+3}}}


Area, {{{77=(1/2)b*a}}}
{{{77=(1/2)b(b+3)}}}
{{{2*77=b^2+3b}}}
{{{b^2+3b-154=0}}}


Can this be factored?  If not use general solution to quadratic formula.
(For checking factorability, look at 154=77*2=7*11*2;  would 14 and 11 work for this?)


LOOK:  {{{(b-11)(b+14)=0}}}
You want the positive solution for b.
{{{highlight(b=11)}}}