Answer:
height = 11.5 in
Step-by-step explanation:
The area (A) of a trapezoid is calculated using the formula
A = h(a + b)
where h is the height and a, b the bases
here a = 21, b = 8 and A = 166.75, hence
h(21 + 8) = 166.75
Multiply both sides by 2 to eliminate the fraction
29h = 333.5 ( divide both sides by 29 )
h = 11.5 in