Machine A working alone can complete a job in 12 hours

Machine A working alone can complete a job in 12 hours. Machine A+B working alone can do the same job in 15 hours. How long will it take machine B working at their respective constant rates to complete the job?

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 #18411