Debra drove to the mountains last weekend. There was heavy traffic on the way there, and the trip took 10 hours. When Debra drove home, there was no traffic and the trip only took 7 hours. If her average rate was 18 miles per hour faster on the trip home, how far away does Debra live from the mountains? Do not do any rounding.

We know that average speed is given by

speed=distance/time

Let the distance between the house of Debra and mountains be 'd'

Let the speed of trip towards mountains be vmph

v= d/t =d/10

Since the average speed on the trip home is given as  thus we have 18 + v

v+18= d/t

v+18=d/7(ii)

Solving equations i and ii  for 'd' we get

d/10+18=d/7

d/7-d/10=18

2d/70=18

d= 9x70= 630 miles

if I'm wrong, I'm so sorry, and I hope this helps! :)

9 x 8 divided by (5-3)=36

maybe i can