The revenue from selling xshirts is r (x) 15x The cost of buying x shirts is c (x) 7x + 20. The profit from selling xshirts is px) x) (x) What is p (x) ?

The profit would be the difference between the total amount earned after selling each and every shirt and the costs of buying them so

p (x) = r (x) - c (x)

7x-20?

The revenue will be the difference between the revenue and the cost.

So if the revenue for X shirts is r (x) = 15x and the cost is c (x) = 7x + 20

the profit will be p (x) = r (x) - c (x) = 15x - 7x - 20 = 8x-20

where you can see that your profit starts to be positive when you sell at least 3 shirts.