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

Question

Tom drove to the mountains last weekend. There was heavy traffic on the way there, and the trip took 9 hours. When Tom drove home, there was no traffic and the trip only took 4 hours. If his average rate was 40 miles per hour faster on the trip home, how far away does Tom live from the mountains?

Answer 1

d_there = r(9)

d_back = _{(r + 40)4}

distances are equal

9r = 4(r + 40)

 

Can you solve for r and ansser?