How many gallons of milk that is 10 percent butter-fat must be…

How many gallons of milk that is 10 percent butter-fat must be added to 8 gallons of milk that is 40 percent butterfat to obtain milk that is 20 percent butterfat?

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 #49841