A can do a work in 3days

A can do a work in 3days. B can do in 6days. If both A&B are working together in how many days they can finish 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 #25530