A Tank is normally filled in 8 hours but takes 5 hours longer to fill because of a leak in its bottom. If the tank is full, the leak will empty it in?

Question: A Tank is normally filled in 8 hours but takes 5 hours longer to fill because of a leak in its bottom. If the tank is full, the leak will empty it in?

Solution:
Let the leak will empty the tank in x hrs.
Total time = 8 + 5 = 13 hrs.

Then,
Or, 1/8 - 1/x = 1/13
Or, (x − 8)/8x = 1/13
Or, 13x − 104 = 8x
Or, 13x − 8x = 104
Or, 5x = 104
Or, x = 20.8