5000 x 1 / 5 = 1000 brochures can fit in one box. Thus, 5000 / 1000 = 5 boxes are needed.
This justifies what answer for what question? Q & A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
A Printing shop needs to ship 5000 brochures to an advertising company. Each box can only contain one-fifth of the brochures. How many boxes are needed to ship those brochures?
5