Elisa walked a certain distance at 5mih and then jogged twic

Elisa walked a certain distance at 5mi/h and then jogged twice that distance a 8 mi/h. Her total time walking and jogging was 2 hr and 15 min. How many miles did she walk?
I am trying to use the formula time= distance/ rate
I set d egual to distance walked at 5mi/h and 2d to distance walked at 8mi/hr
d/5+2d/8=135

Solution

Let d=distance that Elisa walked
Then 2d=distance that Elisa jogged
Amount of time that Elisa walked=d/5
Amount of time that Elisa jogged=2d/8
Now we are told that the above two times add up to 2.25 hr, so:
d/5 + 2d/8=2.25 multiply each term by 40
8d+10d=90 or
18d=90 divide each side by 18
d=5 mi----------------distance Elisa walked
2d=2*5=10 mi--------distance Elisa Jogged
CK
5/5 + 10/8 =2.25
1 + 1.25=2.25
2.25=2.25