Dale drove to the mountains last weekend. there was heavy traffic on the way there, and the trip took 7 hours. when dale drove home, there was no traffic and the trip only took 5 hours. if his average rate was 18 miles per hour faster on the trip home, how far away does dale live from the mountains? do not do any rounding.

If you let X = the distance in miles from Dales's house, and understand rate = distance/ time, the rate going to mountains = x/7, and back from mountains is x/5. If dale was 18mph fast going home, the equation would be...
(coming home rate) = (going to mountain rate) + 18 which is
x/5 = x/7 + 18. Then solve for X.
Use the least common denominator = 35 so multiply everything by 35 and you get...

7x = 5x+630
simplify...
2x = 630, then
x = 315 .
Dale live 315 miles away from the mountains.