Once a month, a professor and his wife drive to Minneapolis, Minnesota to visit their relatives. The distance
between the Cedar Falls, Iowa gas station and their relatives’ house is 222 miles. The couple used to switch off
driving fairly often – they each drove half the time. When they did that, the trip took precisely 3 hours. Once
the professor learned how to grade papers while his wife was driving, he started to drive less during these trips.
His wife started driving for two-thirds of the time. When this happened, the trip took 2 hours 55 minutes.
I need help so I can set up an equation to find the professor's average driving speed.