Explanation:
it is a cube, like the dice in games. just very large.
as such it has 6 equal sides.
so, the surface area is simply the sum of all 6 side areas.
and because all 6 are equally large, we need to calculate only one and then multiply by 6.
the side lengths of this cube are 9 ft.
so the area of one side is then
9×9 = 81 ft²
and the full surface area is then
81×6 = 486 ft²