Penelope made note of all the bicycles and cars she could see parked or locked on a certain city block. All the cars had exactly four wheels, and all the bicycles had exactly two wheels. How many wheels were on the block if there were 7 bicycles and 15 cars? How many wheels were on the block if there were x bicycles and y cars? Total wheels, 7 bicycles and 15 cars: Total wheels, x bicycles and y cars: