Answer:
You should aim slightly east of the enemy ship.
Step-by-step explanation:
The enemy ship is closer to the equator. Because the Earth is round, they have a higher velocity (like how a point on the rim of a spinning wheel moves faster than a point close to the center).
The Coriolis effect is basically just inertia. It says that if you fire the cannonball directly south, that by the time it reaches the point where the enemy ship was, the enemy ship will have drifted with the Earth eastward.
To account for the difference in the speeds of the ships and the inertia of the cannonball, you must aim slightly eastward.