If 12 men or 20 women can do a piece of work…

If 12 men or 20 women can do a piece of work in 81 days, then in how many days can 9 men and 12 women together do the work?

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 #23488