First, break down the problem.
Someone can skate 3 miles in 9 minutes.
What is their speed? How far would they go if they did that speed for 1 minute?
To find speed given time and distance, divide distance by time.
3/9 = 1/3
Speed is 1/3 mile per minute
if they travel one minute, they will travel 1/3 of a mile
hope this helps :)