Hi!
Since the volume of a box is given by l*w*h (so I assume it's a parallelepiped), you have to multiply all the inches of the box.
For example, the small box has x = width, x+2 as lenght and 2x as height.
So you multiply all of them together.
Small box volume: x(2x)(x+2) [expression]
Large volume box: (x+5)(x+7)(3x)
The difference is that the large box contains more things, since it has a bigger volume.
If you solve both expression, you'll find that small box volume is 2x^3 + 4x^2 and that large box volume is 3x^3 + 36x^2 + 105x