Train station

Problem

Every day, Joe arrives at the train station from work at 6pm.
His wife leaves home in her car to meet him there at exactly 6pm, and drives him home. One day, Joe gets to the station an hour early, and starts walking home, until his wife meets him on the road. They get home 20 minutes earlier than usual.
How long was he walking?
Distances are unspecified. Speeds are unspecified, but constant.
Output a number which represents the answer in minutes.

Answer: 50 mins

Solution Approach:

They arrived home 20 minutes early.

The twenty minutes were saved on going to the station and returning home.
so 20/2=10
She drove 10 minutes less each way for a total of 20 minutes. He walked 50 minutes.