Answer:
Slant height = 8 feet.
Step-by-step explanation:
If the perimeter of the square base = 12 then each side of the base = 12/4
= 3 feet and its area = 3*3 = 9 ft^2
The area of one of the triangular sides = 1/2 * 3 * h where h is slant height.
So total surface area = 57 = 9 + 4 * 1.5h
9 + 6h = 57
6h = 48
h = 8 feet.
