Can 3+3 Really Equal 5? The Mathematical Music Question

[pierfrancescopeperoni]

More like (3-1)+(3-1)=(5-1).
Associate an nth to n-1 rather than n, then you can apply regular addition.

[seancregomusic]

The same principle applies to octaves...one octave is 8 notes, but two octaves are 15 notes (not 16) because the octave note is shared and not repeated! It drives music engravers nuts because they want to put 16va instead of 15ma to play two octaves higher (although some editions do use the former, but it's a mistake).

[garycitro]

By extension (or diminution!) a diminished seventh chord computes as 3+ 3+3=6 !!

[Ice_Karma]

I didn't think either one of those things, actually. Instead, when I saw the title, I thought about how three plus three usually equals six, so if you were claiming it equals five, then some kind of... for want of a better word, "shenanigans" must be going on. You piqued my interest, so I clicked to satisfy it. 🤣

[michellebrouellette]

I understood the math as soon as I saw the title

[lawrencetaylor]

That is officially classified as a clickbait title. But it worked. And I knew the answer.
But I did see a symbol on the Fa Clef that I didn't know about. There was the time signature, and then there was a bracket that looked like an Elongated backward C. And it looked like there were two points on it, like the Fa or Sol symbols, and I think they were centered on the Ré line. Any ideas?