A rancher owns a mixture of 8 sheep and 5 cattle that graze on his land. In a typical year, the rancher will allow his animals to feed off his pastures for as long as possible before they run out of grass. After the pastures run out of grass, he must buy feed corn for $10 per bag. Each cow eats 2 acres of grass per month, and each sheep eats 1 acre of grass per month. Additionally, a bag of feed corn can feed each cow for 1 month and each sheep for 2 months.  If the rancher's pasture contains 144 acres of grass, how much will the rancher need to spend on feed corn to feed his animals each year? Let's answer step by step:
First, the 144 acres of grass will be eaten according to the equation 5 * 2 * T + 8 * 1 * T = 144. Solving this equation for T, we find 18 * T = 144, or T = 8 months of food are covered by the animals grazing on the rancher's pasture. This means the farmer must buy feed corn for the remaining 12 - 8 = 4 months. Next, the rancher's 8 sheep will require 4 / 2 = 2 bags of feed corn each, or 8 * 2 = 16 bags of feed corn in total for the 4 month period. The rancher's 5 cows will require 4 / 1 = 4 bags of feed corn each, or 5 * 4 = 20 bags of feed corn in total for the month. Therefore, the rancher needs 16 + 20 = 36 bags of feed corn for all of his animals. So, the rancher will need to spend 36 * 10 = $360 per year on feed corn. The answer: 360.