By walking at 3/4th of his usual speed, a man reaches office…

By walking at 3/4th of his usual speed, a man reaches office 15 minutes later than usual. What is his usual time?

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 #69780