Answer:
35 mi²
Explanation:
Let's subdivide the figure, as shown.
The lower part is a rectangle whose area is (5 mi)(18 mi) = 90 mi².
The upper part is a trapezoid whose area is found by averaging the length and multiplying the result by the width (8 mi - 5 mi), or 3 mi.
Area of trapezoid:
12 mi + 18 mi
------------------------ = 15 mi Width of trapezoid = 3 mi
2
Thus, the area of the trapezoid is (3 mi)(15 mi) = 45 mi²
and the total area of the entire figure is
45 mi² + 90 mi² = 135 mi²