How to solve this question for college

At a book fair, joe bought 24 books at 3 for $5 and had $2 left. how much money did he have at first?

How much money does ron have left each month after his fixed expenses? ron graduated from college five years ago. he recently bought a house, but shares it with a housemate who pays him $800 a month for rent and utilities. ron is putting a budget worksheet together so he will have a better idea of where his money is going and where he can save. enlarge

The speeders soccer team charged $12 to wash each car at a fundraiser car wash.the team collected a total of $672 by the end of the day.how many cars did the deal wash?