Answer:
D.
Explanation:
Doing width times height for a triangle would give you the answer to a whole square, so you must divide it by 2, or multiply by half.
So, 25 x 40 = x, the area of it if it were a square.
Then, since a triangle is cut out, you either divide it by 2 or multiply by 1/2, same thing. That is the area of it.