so, the cube has a cubic hole in the middle.
now, if we nevermind the hole, the volume of the cube, or rectangular prism, is simply the product of its length, width and height, namely 20*20*5, or 2000 cm³.
however, we'll need to subtract the hole from it, and since the hole is another rectangular prism, then its volume is 5*5*5 = 125 cm³.
so if we subtract the volume of the hole from the total volume of the cubic container, what's leftover is just the volume of the cube without the hole, namely
2000 - 125 = 1875 cm³.
