Mr. Smith has $100.00 to buy 100 animals with. Cows cost $10.00 each, pigs cost $3.00 each and chickens cost $.50 each. How many can he buy with exactly $100.00. I have this equation so far, but where do I go from here? 10x + 3y + .5z = 100 Multiply through by 10 to clear decimal: 100x + 30y + 5z = 1000 Divide by 5 20x + 6y + z = 200 x + y + z = 100 19x + 5y = 100 19x = 100 - 5y 19x = 5(20 - y) x = 5(20 - y)/19 Since x is a positive integer, the 19 must divide evenly into 5(20 - y). the 19 will not divide evenly into the 5, so 19 must divide into 20 - y. 20 - y is at most 19, since y must be at least 1. The only integer at least 19 which is divisible by 19 is 19 itself. Therefore 20 - y = 19 -y = -1 y = 1 x = 5(20 - y)/19 x = 5(20 - 1)/19 x = 5(19)/19 x = 5 x + y + z = 100 5 + 1 + z = 100 6 + z = 100 z = 94 Therefore he bought 5 cows, 1 pig, and 94 chickens. Edwin