Answer: 100 ft3
Explanation: The formula for triangular prism in volume is V = Bh. You substitute the B, base, for the area of a triangle, which is bH/2. You multiply by the height of the prism which is 8 ft. The base and height in the triangle’s area formula is 5 x 5 because the triangle is a RIGHT triangle. (which the lines mention) So the sides are equal except for the square. Substitute and solve. You will get the answer.
Hope it helps! Will post a picture of my work below!