Think of it as two rectangular prisms next to each other, and find the volume of each one separately.
The big one on the left has a volume of 4 * 12 * 6, or 288.
The smaller one on the right has a volume of 2 * 6 * 6, or 72.
288 + 72 = 360. 360 cubic feet of water are needed.
It's kind of like division and mutliplycation I guess
