On ITV's Homework Hotline, it's time for "Rudolf's Rules." If you guess what rule Rudolf is using you get a prize. Someone puts
golf balls into a miniature-golf display called Rudolf, then Rudolf sends back a certain number of golf balls. Today Rudolf gets 8 balls and sends back 6. Next Rudolf gets 15 and sends back 27. When he gets 25, 57 are returned. If n represents the number of balls initially given to Rudolf, write an expression to represent how many balls he sent back.