Use the formula you are given and substitute 12 in. for L, 9 in. fo W, and 2 in. for H. Then evaluate it.
S = 2(LW + WH + HL)
S = 2[(12 in.) * (9 in.) + (9 in.) * (2 in.) + (2 in.) * (12 in.)]
S = 2[108 in.^2 + 18 im.^2 + 24 in.^2]
S = 2[150 in.^2]
S = 300 in.^2
Answer: A. 300