A cask P is filled with 50 liters of water, and cask Q with 40 liters of acid. Precisely x liters are drawn from each cask and then, mixed and replaced. The same operation is then repeated.

Accordingly, the foregoing operation is performed precisely 2 times.

After the conclusion of the 2nd operation, precisely 8.875 liters of acid remain in cask P.

Determine the value of x.