Jean stocked her aquarium with 36 fresh-water fish, which cost $212. The male fish cost $5 each, while the female fish cost $7. Find the number of male fish and the number of female fish.

For this question, we need to translate into equations to solve it. There are total 36 fish (male and female). Let's say we have x male and y female. Then x+y=36.

We know the total cost is $212, $5 for each male and $7 for each female, thus, the relation is 5x+7y=212.

Now, we solve the system:

x+y=36

5x+7y=212 to get x=20 and y=16. Which means the number of male fish is 20 and the number of female fish is 16.