If it takes her 1/6 per hour to run half a mile. Let's see how long she can run in one hour.
To get from 1/6 hour to 1 hour .. we need to multiply by 6.
6 * 1/6 = 1
We will now also need to multiply her distance by 6
1/2 * 6 = 6/2 = 3
Now we know she runs 3 miles in one hour. Which is also her speed. 3mph