Check the picture below.
first off let's check what "h" is in the triangular face.
so, the gazebo has 4 squarish faces, each 12x12, recall 48 ÷ 4 = 12, and it has 4 triangular faces, each with a height of 8 and a base of 12.
notice we're skipping the top and bottom of the cube and the bottom of the pyramid because they're not part of the "surface area".