Let x = number of male fish
Let y = number of female fish.
We need to construct a system of equations to solve this problem.
36 = x + y
212 = 5x + 7y. Lets solve this by elimination. Multiply the first equation by -5
-180 = -5x + -5y
212 = 5x + 7y. Now we need to add the equations together.
32 = 2y. Divide each side by 2.
16 = y. Plug this number into one of our original equations.
36 = x + (16). Subtract 16 from both sides.
20 = x.
There are 20 male fish and 16 female fish.
