Which of the following justify why she used the mean instead of the median

Agreeting card company can produce a box of cards for $7.50. if the initial investment by the company was $50,000, how many boxes of cards must be produced before the average cost per box falls to $10.50?

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base