Answer:
2.6 m
Explanation:
The surface area for rectangular prisms is: S = 2lw + 2lh + 2wh, where l = length, w = width, h = height.
Substitute the known values into this equation: h = 5, l = 10, w = x, S = 178
178 = 2(10x) + 2(5 x 10) + 2 (5x)
Simplify!
178 = 20x + 100 + 10x
Subtract 100 from both sides and combine x's
78 = 30x
divide both sides by 30
x = 2.6 m
answer check: 2(10 x 2.6) + 2(5 x 10) + 2 (5 x 2.6) = 178 (true!)