I had to look up several sources to understand how to calculate a percentage. I wrote down and made examples and I still have issues if I do not look at what I wrote down about how to.
This guy probably took a glance at the problem and had it figured out right away but did not want to embarrass the others so he said it took him one day to figure out.
As I said, this goes for music and art as well. A friend of mine who was studying to be a music conductor picked up my Celtic harp I never could figure out how to play, tuned it up and started playing like a pro. He never played a harp before.