1 mile is equivalent to 5280 feet. Then:
1 mile / x miles = 5280 feet / 18 feet
x = 1*18/5280
x = 0.0034 miles is equivalent to 18 ft
1 hour is equivalent to 3600 seconds, then:
1 hour / x hours = 3600 seconds / 2 seconds
x = 1*2/3600
x = 0.00056 hours is equivalent to 2 seconds
The speed is computed as follows:
speed = distance/time
Replacing with data:
speed = 0.0034 miles/0.00056 hours
speed = 6.07 miles/hour