A solid cube of 4 inches has been painted red, green and black on pair of opposite faces. It has been cut into one inch cubes. How many cubes have only two faces painted?

As per the given all information in above question , we can say that
There are 8 cubes in Layer 1, 4 cubes in Layer 2, 4 cubes in Layer 3, and 8 cubes in Layer 4 which have only two faces painted.
Thus, there are 8 + 4 + 4 + 8 = 24 such cubes.