Answer:
135 mi²
Explanation:
We'll divide this figure into two parts, a rectangle and a trapezoid, find the area of each of the two parts, and then add the results together to find the whole area.
The area of the rectangular base is A = (length)(width)
= (18 mi)(5 mi) = 90 mi²
The area of the trapezoid is A = (average length)(width)
12 mi + 18 mi
= ( ----------------------- )(8 - 5) mi
2
or: A = (15 mi)(3 mi) = 45 mi²
The total area is thus 45 mi² + 90 mi² = 135 mi²