There were some people on a bus. Half of the people get off at the first stop and 11 people get on. Now there are 20 people on the bus. How many people were on the bus to begin with?
this is because in order to find out how many were on the bus, you simply do 20 - 11 = 9. Than you must multiply 9 by 2 which equals 18. That gives you your answer.
