A motor boat travelling at the speed can cover 25 km in 8 hours .At the same speed it can travel 35 km upstream and 52 km downstream in 11 hours .The speed of the stream is
Also, is "to travel at the speed" some nautical expression, or is some phrase skipped there?
The point of my post is that it is not enough to copy a problem statement without even bothering to say what you want to be done with it. Have you tried solving it? What is the difficulty you encountered?
If the boat has speed "v" in still water and the stream has speed "s", then the speed of the boat upstream (relative to the shore) is v- s and downstream v+ s. To travel 35 km upstream at speed v- s km/h requires 35/(v- s) hours. To travel 52 km downstream at v+ s km/h requires 52/(v+ s) hours. We are told that the total time is 11 hours: 35/(v- s)+ 52/(v+ s)= 11.
Since the "boat travels 24 km in 8 hours" (I assume this is in still water), you can determine v and then have a single equation in the single variable s.