The front face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
The back face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
The left face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
The right face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
The top face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
The bottom face of the cube is a 2 by 2 square, so its area is 2×2 or 4.
Add all those areas of the 6 faces up and you get 4+4+4+4+4+4 = 24.
Edwin