Jonathon and Samantha row their canoe 24 miles downstream in 2 hours. After a picnic, they row back upstream. After 3 hours they only travel 12 miles. Assuming that they canoe at a constant rate and the river's current is constant, find the speed at which Jonathon and Samantha can row in still water. The speed at which Jonathon and Samantha can row in still water is miles per hour.