You're on a bus. 20 people get on at the first stop. At the next stop 45 people get on. At the 3rd stop 48 people get off. Then at the next stop 5 people get off and 9 get on. At the last stop 21 people get off 2 people are left. How is this possible? (Who's still on the bus)!?
This is possible because you and the bus driver are still on the bus!