If A is thrice as fast as B and together can do…

If A is thrice as fast as B and together can do a work in 12 days. In how many days A alone can 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 #22603