Answer: 9 miles
Step-by-step explanation:
The distance would be 9 because if the speed walker walked 4.5 miles in 3/4 of an hour, he would be going 6 mph (miles per hour).
If he walks twice as fast, he would be going 12 mph.
If he walks for 3/4 of an hour (45 minutes) at 12 mph, he would walk 9 miles.
