At a fair each ride costs one two or four tickets. The numberof rides that cost

At a fair each ride costs one two or four tickets. The numberof rides that cost two tickets is three times the number of ridesthat cost one ticket. Also seven more rides cost four tickets thantwo tickets. Kimberly who has a book of tickets goes on a ride atrandom. If the probability that the ride cost her four tickets is4/7 how many rides are there at the fair?