If you would like to know your average speed per hour, you can calculate this using the following steps:
1 1/2 miles = 3/2 miles ... 12 hour
x miles = ? ... 1 hour
3/2 * 1 = 12 * x
3/2 = 12 * x
x = 3/2 / 12
x = 3/2 * 1/12
x = 3/24
x = 1/8 miles per hour
The correct result would be 1/8 miles per hour.