As there is no information about the speed of the ferries, we can infer that they move at the same speed.
Therefore, we can say that they cross each other at the same point both on their way and on their way back.
Since the "meeting point" is on a streight line in between the two shores, 100 meters from shore B and 50 meters from shore A, the distance between shore A and B will be 100 + 50 = 150 meters.
Hence, the distance between shores A and B is 150 meters.
