Ships On Water: Problem 3

Problem: There is a wide river. The water speed at the middle of the river flows 8 kilometers per hour, and at the coast of the river the water flows 6 kilometers per hour. A ship sailing down the river from the middle takes 13 hours to sail 520 kilometers. If it wants to go back to where it started, sailing along the coast of the river, how many hours would it take?

The Distance Rate and Time Series: https://youtube.com/playlist?list=PLytgs3PKtgQ505ltfvVSH5dabJhRKC_IN

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