The concert lasts 60 minutes, and the songs are all the same length. the choir sings a total of 12 songs, 2 of which are sung by the sopranos only. for how many minutes do the sopranos sing by themselves? solve the equations using a letter for the unknown quantity.

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?