If you would like to know Johnathan's average speed in miles per hour, you can calculate this using the following steps:
3 2/3 = 11/3 miles ... 7/8 hour
x miles = ? ... 1 hour
11/3 * 1 = 7/8 * x
11/3 = 7/8 * x
x = 11/3 * 8/7
x = 88/21
x = 4 4/21 miles
The correct result would be 4 4/21 miles per hour.