Of the 800 participants in a marathon 120 are running to raise money for a cause how many participants out of 100 are running for a cause

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