Question

a bus has a maximum capacity of 70 passengers. There are 28 riders on the bus. What are all the possible numbers of riders, r, who canget on the bus if no riders get off

Answer 1

42 passengers are able to still get on

Answer 2

70 is the total amount of passengers there can be. There are already 28 on the bus and they are not getting off. Therefore you take 70 minus the passengers already on the bus which is 28, and you get the amount of passenger that can get on. 70-28=42.
Answer: 42 passengers can still get on.