A recipe for a seafood casserole calls for crab meat, shrimp, and rice. Crab meat costs $5.50 per pound, shrimp costs $4.50 per pound, and rice costs $0.80 per pound. You want to make a 7lb casserole, which will cost you $19.80. The recipe states that the amound of rice should be equal to the combined amount of crab meat and shrimp. How much of each ingredient should be used?
Im in algebra 2 with trigonometry. And i have to solve this using: systems of equations: substitution, elimination, cramer's rule.

Question

A recipe for a seafood casserole calls for crab meat, shrimp, and rice. Crab meat costs $5.50 per pound, shrimp costs $4.50 per pound, and rice costs $0.80 per pound. You want to make a 7lb casserole, which will cost you $19.80. The recipe states that the amound of rice should be equal to the combined amount of crab meat and shrimp. How much of each ingredient should be used? 
Im in algebra 2 with trigonometry. And i have to solve this using: systems of equations: substitution, elimination, cramer's rule.