Liza reads 20 pages in an hour, and Suzie reads 15 pages in an hour. How many more pages does Liza read than Suzie in 3 hours? Think carefully first, then make a decision:
In 3 hours, Liza reads 20 x 3 = 60 pages. In 3 hours, Suzie reads 15 x 3 = 45 pages. Liza reads 60 - 45 = 15 pages more than Suzie. So, the answer is 15.