1. Joann's equation is J = 25h
2. Bill's equation is B = 50(h - 0.75), since he left 45 minutes (0.75 hours) after Joann.
3. Joann traveled J = 31.25 miles (25 x 1.25 hours) and Bill traveled B = 37.5 miles (50 x 0.75 hours) when 1 1/4 hours passed since Joann left the dock.
4. It took Joann 2 hours (50 miles / 25 mph) to reach the dam. Since Bill left 45 minutes later, it took him 1 hour and 15 minutes (50 miles / 50 mph = 1 hour, 0.5 hours or 30 minutes) to reach the dam after Joann.
5. Joann was between 10 and 15 miles from the dam during the time interval 0.4 hours (10 / 25) < h < 0.6 hours (15 / 25).