A pet shop bought a litter of puppies for $120. All but four of them were sold, a a profit of $5 each, for a total of $120. How many puppies were in the litter.

Answer 1

Let x be the number of puppies in the litter.
Cost per puppy = 120/x
Revenue per puppy = 120/(x - 4)
Profit per puppy = 5
Profit = Revenue - Cost
Plug in the above expressions and solve.