The wording here is quite poor ("crosses a boat" is unintelligible), but I think the idea is something like

A ship of length 300 meters is traveling upstream at a constant rate on the Suez Canal, which has its own constant rate of 10 km/h. The ship encounters a boat, which is floating freely down the Canal. (Assume the boat has zero weight, and is traveling only under the power of the stream.) If the time from when the ship meets the boat to when the ship passes the boat is 30 seconds, what is the speed of the ship in still water

Let's call the ship's rate in still water s. We know that

(Ship's Rate + Boat's Rate) * 30 seconds = 300 meters

since the ship and the boat are working together to traverse the full 300 meters. (The ship is doing one part of the distance, and the boat is doing the rest, so we can add their rates together.)

We also know that the ship's rate against the current = (s - 10), and the boat's rate with the current is 10, so we have

(s - 10 + 10) * 30 seconds = 300 meters

s = 300 meters/30 seconds = 10 meters/second

To convert this to kilometers per hour, we multiply the top by 60*60 and the bottom by 100, which gives us 36 kilometers/hour.

That said, I'm not sure my interpretation is correct ... but it does get me to the OA, and seems like the intent of the question!