The distance from Greentown to Glenavon is D1 = g*(15+x) miles downstream. The distance from Glenavon to Cambria is D2 = g*(15-x) miles upstream. The difference D1 - D2 is 2 miles, according to the condition. It gives you an equation g*(15+x) - g*(15-x) = 2, which you can easily solve and find "x", the rate of the current. x =miles per hour.