Answer :

iGreen
Divide the miles he traveled by the time it took him to travel it.

22 1/2 / 1/3

Multiply by the reciprocal of 1/3:

22 1/2 * 3/1

Convert 22 1/2 into an improper fraction:

45/2 * 3/1

Multiply the numerators and denominators together:

135/2

Divide:

67.5 or 67 1/2

So his average speed in miles per hour is 67 1/2.
If he has travelled 22 1/2 miles in 1/3 of an hour, all you need to do is multiple his travelled distance by 3 to see how far he would have go in one hour. 

22.5 x 3 = 67.5

So Kevin travelled at 67.5mph