A can do a work in 6 days

A can do a work in 6 days. B can do the same work in 12 days. If both A & B are working together in how many days they will 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 #37369