For cases like these, we need to find the base then multiply it by the height. Let’s separate the triangle and the rectangle of the base
Triangle:
1/2(6*9) = 27
Rectangle:
5 * 9 = 45
Total base:
45+ 27 = 72
Now for the area:
72 * 12 = 864 m^3
864 m^3 would be the volume.
