Let us first find the result in miles per hour. 100 miles / 2 hours = 50 mph. To convert to minutes, we will use the unit conversion factor [1 h / 60 minutes]. So we get the expression:
[50 miles / 1 hour] x [ 1 hour / 60 minutes]
The hours unit will cross cancel and we will get:
[50 miles / 60 minutes ] = 5/6 miles per minute or 0.8333... mi/min
Hope this helps :)