Answer: there are 11 cows
Step-by-step explanation:
Let x represent the number of chickens in the farm.
Let y represent the number of cows in the farm.
If the farm has 30 chickens and cows, this means that
x + y = 30
There are 82 chicken and cow legs all together. A chicken has 2 legs. A cow has 4 legs. This means that
2x + 4y = 82 - - - - - - - - - - - - 1
Substituting x = 30 - y into equation 1, it becomes
2(30 - y) + 4y = 82
60 - 2y + 4y = 82
- 2y + 4y = 82 - 60
2y = 22
y = 22/2 = 11
Substituting y = 11 into x = 30 - y, it becomes
x = 30 - 11 = 19
