It will take 2 hours to meet.

Method 1: Ignore the speed of the stream, as the bobber will be carried along at three miles per hour as will you. It takes two hours to travel fourteen miles, at a rate of seven miles per hour.

Method 2: As the bobber travels at 3 mph, it will be six miles closer to you in two hours. The distance between you and the bobber becomes 8 miles (14 – 6). In two hours you would have travelled 8 ( (7-3) x 2 ) miles.