The area of a trapezoid is computed as follows:
A = h*(a + b)/2
where h is the height, and a and b are the length of the bases.
One base of the trapezoid is 6 inches longer than the other base, then:
a = b + 6
Replacing with A = 96, h = 8, and a = b + 6, we get:
96 = 8*(b+ 6 + b)/2
96 = 8*(6 + 2b)/2
