farmer joe needs cows pigs an chickens

Question

cows cost 10.00 each and pigs cost .50 cents each,an chickens are 10 cents.he needs 100 animals an he only has 100 dollars .

let x=cow, y=pig, and z=chicken
10x + .5y +.1z = 100
x + y + z = 100

substitute & get the answer.