Answer:
6(base) x 3.5(Height) = 21, 21 divided by 2 (x 1/2) = 10.5
10.5(area of triangle) x 7.75(width) = 81.375
Formula of an area of a triangle:
BH x 1/2
Base x Height x 1/2(basically just dividing by 2)
Now the base:
1.5 x 7.75 x 6 = 69.75
Now let's add the two given volumes:
81.375+ 69.75 = 151.125 ft^3 is your answer.