9. Jenny is selling t-shirts to raise money for the cheerleading team. She sells long sleeve t-shirts for $18 and short sleeve t-shirts for $12. At the first football game Jenny sells 54 t-shirts and
makes $774. Write and solve a system of equations to find out how many of each she sold.
(let x=the number of long sleeve t-shirts and y=the number of short sleeve t-shirts)