if i have sold 31 pies and made 13 dollars how much does one pie cost

Answer 1

31x where x = cost of one pie in dollars = cost to the customer

31x = 13

x = 13/31 = $4.03 per pie

13 x 4.03 = $13 = gross revenue to you, the pie peddler

but this doesn't take account of cost of making the pies

subtract that to get your profit

if this is a problem from a microeconomics, business or finance course, you need more info

if this is "just" an algebra or math course, then: go with $4.03 per pie