A can do a job in 15days and B in 30days

A can do a job in 15days and B in 30days. If they work on it together for 4 days, then the fraction of the work that is left is?

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 #90004