Respuesta :

You would start of by doing
A=1/2bh
—. ——. <—-Divide
B. B

After that you will end up with
AB=1/2H

Then isolate the B by dividing both sides by A

AB=1/2h
—- ——
A. A

Which will leave you with your answer of

B=1/2ha or B=1/2ah