The parallelogram area formula is b*h just like a square but the height is the distance from the base to the parallel top .. not the side length.. that's the only difference.
the base is x+4
total area is 5x+20
so use those in our formula
area = b*h
5x+20 = x+4 * h now solve for h (yes we'll have an x in the other side, but that's okay b/c their formulas do also)
