In the tank from which water is taken for rabbits 40 tons of water

In the tank from which water is taken for rabbits 40 tons of water, 8 tons of water are poured every morning and 4 tons are added in the evening, after how many days will the tank be empty?

In the problem it is given that there were 40 tons of water in the tank. Every morning they take 8 tons of water, and in the evening they add 4 tons of water, that is, 8 – 4 = 4 tons of water are consumed per day.

So, as the problem asks: in how many days the tank will become empty, that is, in how many days it will take 40 tons of water.

And this will happen in 40/4 = 10 days.