A and B can do a piece of work in 7 days

A and B can do a piece of work in 7 days. With the help of C they finish the work in 5 days. C alone can do that piece of work in?

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 #404