Walking with 4/5 of my usual speed, I arrive at the bus…

Walking with 4/5 of my usual speed, I arrive at the bus stop 9 minutes later than normal. How many minutes does it take to walk to the bus stop at my usual speed?

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 #32629