X to the 8/15 power. When you have a power raised to another power, you multiply the exponents.
Surface area of a cuboid
= [2(length)(width)] + [2(width)(height)] + [2(height)(length)]
= {[2(4)(2.5)] + [2(2.5)(2)] + [2(2)(4)]} units²
= (20 + 10 + 16) units²
= 46 units²
