Overview
I'm working on a mathematics question and need the explanation and answer to help me learn.
The Landmark College office started with one old copy machine. After a while, they bought a new copy machine. The new copy machine can xerox one box of student files in 1 hour. The old machine can xerox the same amount of paper in 3 hours. How long will it take to xerox one box of student papers if Landmark College office runs both copy machines at the same time? How can you be sure that your answer is right?