We are given two figure, i) Cube, ii) rectangular box
The volume of any shape is calculated by multiplying height, width, length.
Volume = height x length x width
In the case of a cube, all the dimensions are the same. So volume would be = length x length x length
here, length = 6
So,
V(cube) = 6^3
For a rectangular box:
V(rect) = height x length x width
V(rect) = h x 12 x 6
As given, V(cube) = V(rect). Therefore,
6^3 = h x 12 x 6
Hence, the first option is correct.