Answer: 5 hours
Explanation:
Andy speed = 7.5/3 = 2.5 mph
William speed = 15/4 = 3.75 mph
1. Write an equation that represents the question
let h = # of hours it takes William to catch up with andy
2.5h + 6.25 = 3.75h
2. subtract 2.5h from both sides
6.25 = 1.25h
3. Divide 1.25 from both sides
h = 5
Therefore, we know it will take 5 hours for William to catch up with andy.