a group of friends is on a rafting trip. they plan to travel 5 miles downstream and then 5 miles back upstream. they need to finish their rafting trip in 6 hours to allow enough time to get back to their hotel. the group knows that the river is moving at a rate of 2 miles per hour. part a question let x represent the speed of the raft when it is in still water. what rational equation represents this situation? use the relationship time