A boat traveled 60 miles downstream and back. The trip downstream took 3 hours. The trip back took 6 hours. Find the speed of the boat in still water and the speed of the current.
As boat travelled 60 miles downstream in 3 hours it's speed is 60/3=20 miles per hour.
And as it travelled 60 miles upstream in 6 hours it's average speed upstream is 60/6=10 miles per hour.
Speed of boat in still water = x miles per hour and speed of current = y miles per hour.
Speed downstream would be x+y miles per hour and speed upstream would be x−y miles per hour.
x+y=20 and x−y=10
Add both together: x+y+x−y=20+10
2x=30 or x=30/2=15 and y=20−15=5
The speed of the boat in still water is 15 miles per hour and speed of current is 5 miles per hour.
This sounds right to me but CPhill probably has a better answer.