Question 835080
{{{A=(1/2)*h(b+B)}}} for B
multiply each side by 2
{{{2A=h(b+B)}}}
distribute
{{{2A=hb+hB}}}
add -hb to each side
{{{2A-hb=hB}}}
divide each side by h
{{{(2A-hb)/h=B}}} or {{{2A/h-b)}}}={{{B}}}