Solving a distance, rate, time problem using a linear equation

Question

Justin drove to the mountains last weekend. There was heavy traffic on the way there, and the trip took 7 hours. When Justin 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 justin live from the mountains?

Answer 1

5 (x+18) = 7 x   ⇒ x=45

 

distance = 45*7 = 315 mi