What quantity of water should taken out to concentrate 12 liters of…

What quantity of water should taken out to concentrate 12 liters of 40% acidic liquid to 60% acidic liquid?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #38701