The volume for a cube is length x width x height.
V = L*W*H
Substitute V with the volume:
1728 = L*W*H
Because it is a cube, we know that the length, width, and height will all be equivalent. Let's say that L, W, and H are all x.
1728 = x*x*x
We know that x times x times x is really just x cubed.
1728 = x³
We must cube root both sides.
You should get 12,
that means that 12 x 12 x 12 = 1728 :)