How much time would it take a person to walk 6 miles at a speed of 3 mi/hr?

2 hours

We can write the problem like this:

3 mi/1 hr = 6 mi/x hrs

Then we can cross multiply to get 3x = 6. This gives us x = 2 hrs.

A train travels 40 miles west in 2 hours. What is it's velocity?