Answer:
So if you know that you can complete 6 miles over the course of 30 minutes it is just matter of multipling 30 minutes times 4, this is becasue it takes 4 times your base distance and time to get to yur goal of 24 miles.
30 x 4 equal 120
which you divide by 60 (because you have 60 minutes in one hour)
so it is safe to say that it will take 2 hours of 120 minutes to ski a ditance of 24 miles at a speed of 6 miles per 30 minutes.
Hope this helps!