The answer is 73.5 inches squared.
To find this answer, you need to subtract the non-shaded area (triangle) from the whole rectangle to get the shaded area.
You can find a triangle's area by first multiplying the base and height, then dividing that by 2. The base and height are 21 and 7 respectively, so we multiply them to get 147 inches squared. Then we divide that by 2 to get 73.5 inches squared.
Now, the rectangle is equal to base times height, and we've already done that with the same lengths for the triangle: 21 and 7. The area of the rectangle is therefore 147 inches squared.
147-73.5 = 73.5, therefore the answer is A.
