The boat moves from point a to point b along the river against the current and spends 4 hours for the entire journey

The boat moves from point a to point b along the river against the current and spends 4 hours for the entire journey. On the way back, it spends 3 hours, moving at the same speed. How many hours will it take for the log to swim from point c to point a?

Let the speed of the boat be x km / h and the speed of the current y km / h. Since sailing with the current, the boat travels the same distance as against the current for an hour faster, we get the following equation:
4x – 4y = 3x + 3y
x = 7y
(3x + 3y) km = 21y + 3y = 24y (km) – the distance between points A and B.
24u km / y km / h = 24 (hours) – the time during which the log will swim from point B to point A.
Answer. On the way from point B to point A, the log will spend 24 hours.