The two ships travel at the same speed. The first is exactly to the west. In what direction

The two ships travel at the same speed. The first is exactly to the west. In what direction is the second ship moving if it seems to an observer on its deck that the first ship is motionless?

Here is a vivid example of the so-called “frame of reference” When two bodies move with the same speed and in the same direction, then it is assumed that in this frame of reference both objects are motionless or stand still. Here, however, such a system is clearly and it is clear that the second ship is also moving to the west.