Tim and a friend left a campsite on a trip down a river in a canoe, maintaining a constant speed of 4 miles per hour. Four hours later, Tim's father set out after them in a motorboat carrying the camping supplies. The motorboat traveled at a rate of 12 miles per hour. How long after he started did Tim's father overtake the boys?
It takes a passenger train 2 hours less time than it takes a freight train to make the trip from Brownsville to Greentown. If the passenger train averages 60 miles per hour on the trip while the freight train averages 40 miles per hour on the trip, how far is it from Brownsville to Greentown?