Final answer:
Using a system of equations representing the number of legs and heads, we determine that Farmer John has 12 cows and 36 chickens on his farm based on the provided totals of 120 legs and 48 heads.
Step-by-step explanation:
Farmer John has cows and chickens on his farm. We're tasked to determine the number of each animal given the total number of legs and heads. The number 120 legs represents the total legs of cows and chickens combined, with cows having 4 legs each and chickens having 2. The number 48 heads simply represents the total number of animals since each animal has one head.
To set up a system of equations, we denote the number of cows as c and the number of chickens as h. Since each cow has 4 legs and each chicken has 2, and together they have 120 legs, our first equation is 4c + 2h = 120. Since there are 48 animals in total, our second equation is c + h = 48.
Solving the system using substitution, we first solve the second equation for c, getting c = 48 - h. Substituting this into the first equation gives us 4(48 - h) + 2h = 120. Simplifying, we get 192 - 4h + 2h = 120, which reduces to 2h = 72. Therefore, h = 36. Substituting h back into c = 48 - h gives us c = 48 - 36 = 12. Consequently, Farmer John has 12 cows and 36 chickens on his farm.