What times what equals 15

Choco pies are cookies made from chocolate (c), sugar (s), and flour (f). chocolate costs $5 per pound, sugar costs $3 per pound, and flour costs $2 per pound. you spend $50 on 18 pounds of food and buy twice as much flour as sugar. calvin wants to invest $12,000 in deposits. for tax purposes, he wants his total interest to be $600. he wants to put $1000 more in a 2-year deposit than in a 1-year deposit and invest the rest in a 3-year deposit. how much money should he invest in each deposit?