Using A=bh slove for h

Bassically you divide A (the area) by the B (the base) to get H (height)

Solve A = bh for b. Since h is multiplied times b, you must divide both sides by h in order to isolate b. Since (c+d) is divided by 2, you must first multiply both sides of the equation by 2. Then you have to subtract c from both sides in order to isolate d.