Suppose you want to make a certain kind of tropical punch,

Suppose you want to make a certain kind of tropical punch, using bananas, oranges, and papayas. You don't know how many of each to put in the punch, but you know that there are seven pieces of fruit in the mix, and there are twice as many oranges as bananas. You also know that the seven pieces of fruit cost $5.25, where bananas cost$.50 each, oranges cost $.75 each, and papayas cost$1.25 each. How many of each bananas, oranges, and papayas you must put in the punch?