For the volume of a rectangular prism (box-shape), all we have to do is multiply, length * width * height.
We know from the text that the hole the construction company will be digging is 12 yards long, 7 yards wide, and 3 yards deep, so all we need to do to find the volume of the dirt removed in cubic yards is multiply, 12 * 7 * 3.
12 * 7 = 84
84 * 3 = 252
The construction company will have removed 252 cubic yards of dirt for the swimming pool.
Hope that helped! =)