13. $400 Carmen has 19 free passes to a concert. If she keeps one for herself and divides the rest equally among three friends, how many will each friend have?
55. $500 The fourth grade class had a read-a-thon. Ed read 2 chapters of a book in the first week. Each week after that, he read 2 more chapters than the week before. How many chapters did he read in the SIXTH week?
68. For homework on Monday evening, Charles spent 25 minutes reading a novel and 20 minutes working on math problems. Usually, Charles spends 1 hour and 15 minutes doing homework. How much time has Charles saved doing his homework?