Question 65183
{{{A=(1/2)h(B+b)}}} for b
{{{2A=2(1/2)h(B+b)}}}
{{{2A=h(B+b)}}}
{{{2A=Bh+bh}}}
{{{2A-Bh=Bh-Bh+bh}}}
{{{2A-Bh=bh}}}
{{{(2A-Bh)/h=bh/h}}}
{{{b=(2A-Bh)/h}}}
There is a couple of way to have done this that would give you slightly different looks, but they would be equivalent to this.  If your answer looks like {{{b=2A/h-B}}} you're right too.
Happy Calculating!!!