math
posted by bill on .
farmer fred had chickens and cows on his farm. he knows that together there are 108 legs and 30 heads. how many of each type of animal does he have?

c chickens have 2c legs
m cows have 4m legs
c+m = 30
2c + 4m = 108
multiply the top equation by two, and subtract
2c + 2m = 60
2c + 4m = 108
2m = 48
m = 24
c = 6