Explanation:
area of trapezoid = 1/2 × (a+b) h
where a = long base
b = short base
h = height
given that, a = 8, b = 5, a of trapezoid = 104:
area of trapezoid = 1/2 × ( 8+5) h
104 = 13/2 h
104 * 2 = 13 h
13 h = 208
h = 208 / 13
h = 16.0 ft.
hope this helps you!
-s.