So the formula to find the surface area for a rectangular prism is A = 2 (w l + h l + h w).
(• is for multiplication)
First, you enter the numbers into that formula. The width is 3, the length is 15, and the height is 4. So it becomes: A = 2 (3•15 + 4•15 + 4•3). Enter that into the calculator and your answer is 234, or if you really want it step by step:
A = 2 (45 + 60 + 12)
Then calculate that.
A = 2 • 117
117 • 2 = 234