Final answer:
Matthew walked a total distance of 3 miles in one hour, so his speed is 3 miles per hour (mph).
Step-by-step explanation:
The question asks for Matthew's speed in miles per hour after he walked 9 laps around a track where each lap is 1/3 of a mile. To find Matthew's speed, we first need to calculate the total distance he walked, by multiplying the number of laps (9) by the distance of each lap (1/3 of a mile), which gives us 3 miles.
Since Matthew completed this distance in one hour, his speed is simply the total distance divided by the total time. Therefore, Matthew's speed is 3 miles per 1 hour, or simply 3 miles per hour (mph).