Yesterday, dustin biked 4 1/2 miles, jogged 2 3/4 miles, and swam 3 1/8 miles. how many miles did he travel while exercising?

Yesterday during the exercise Dustin spent time on three exercises:

1) Bike.
Distance Covered =  miles

2) Jogging
Distance Covered =  miles

3) Swimming
Distance Covered =  miles

The Total distance covered during the exercise will be the sum of distance covered during each activity.

So,

Total Distance Covered during exercise = 4.5 + 2.75 + 3.125 = 10.375 miles

Thus, Dustin covered 10.375 miles yesterday while exercising. 

I’m confused what’s happening