Question

There are 17 animals in the barn. Some are chickens and some are cows. There are 56 legs in all. How many of each animal are there?

Answer 1

6 chickens, 11 cows.

Explanation:

x - chickens

y - cows

x + y = 17

2x + 4y = 56 <-- chickens have 2 legs, cows have 4.

y = -x + 17

Substitute (-x+17) for y in the second equation.

2x + 4(-x + 17) = 56

2x -4x + 68 = 56

2x = 12

x = 6 chickens

Now substitute 6 for x

6 + y = 17

y = 11 cows