Today, joelle walked 20 minutes at a rate of 3 miles per hour, and she ran 15 minutes at a rate of 6 miles per hour. how many total miles did joelle travel while walking and running? have a descriptive explanation. : )

Joelle walked for 20 minutes and her speed was 3 miles per hour.
So
In 1 hour or 60 minutes Joelle walked for a distance of = 3 miles
Then
In 20 minutes Joelle walked for = (3/60) * 20 miles
                                                   = 60/60 miles
                                                   = 1 mile
Again
Joelle ran for 15 minutes at a speed of 6 miles per hour
So
In 1 hour or 60 minutes Joelle walked for a distance of = 6 miles
so
In 15 minutes Joelle walked for a distance of = (6/60) * 15 miles
                                                                         = 15/10 miles
                                                                         = 3/2 miles
So 
The total distance covered by Joelle = 1 + (3/2) miles
                                                           = (5/2) miles
                                                          = 2 1/2 miles
So Joelle covered a total distance of 2 1/2 miles while walking and running.