The distance from his house to the gas station is 5 miles. We can find this by counting out the number of spaces between the two points (since the chart indicates that 1 unit = 1 mile). Or we can subtract the x coordinates to get 8-3 = 5. This only works because the y coordinates of each point are the same value.
To find the distance from the gas station to the market, we subtract the y coordinates this time. This only works due to the x coordinates being the same. We get a distance of 8-3 = 5 miles.
Overall, the total distance Byron drives is 5+5 = 10 miles.
