The definition of average speed is
(total distance covered) divided by (time to cover the distance) .
If you didn't remember that, you can still solve the problem
if you Use your units !
You want a number that has units of [ mile / minute ].
That's what you get if you divide the miles by the minutes.
Average speed = (15 miles) / (70 minutes)
= ( 15 / 70 ) miles/minutes
= 0.214 mile / minute (rounded)
