Hello, mirdita59!

Welcome aboard!

A hospital needs to dilute a 60% boric acid solution to a 10% solution.

If it needs 40 liters of the 10% solution, how much of the 60% solution

and how much water should it use?

Let = amount of 60% solutions to be used.

Then = amount of water to be used.

Consider the amount of boric acid in each stage.

We used liters of the 60% solution.

. . This contains: liters of boric acid.

We add liters of pure water.

. . This contains: liters of boric acid.

The mixture contains: . liters of boric acid.

But we are told that the final 40 liters should be 10% boric acid.

. . Hence, it will contain: . liters of boric acid.

There is our equation: .

Therefore, we should use liters of the 60% solution and liters of water.