A ship sails from ' X' to ' Y' on a bearing of 240°. On what bearing will it have to sail to return from 'Y' to 'X'

A back bearing is the bearing from the destination back to the starting point. If you know the bearing from point A to point B, the back bearing is the bearing from point B to point A.

To find the back bearing, if the original bearing is less than 180°, add 180°. If the original bearing is greater than 180°, subtract 180°.
The given bearing is 240°, which is greater than 180°.

Back bearing = Original bearing - 180°
Back bearing = 240° - 180°
Back bearing = 60°

The ship will have to sail on a bearing of 60° to return from Y to X.