Well, there isn't a word for 99 in Spanish or English, in both languages we say 90+9, so that counts as maths.

If you are asking about words for 70, 80 and 90, that is a peculiarity of French, and not even all dialects, some dialects have septante, huitante/octante and nonante for those.

haha no

It's just the French being weird, there's even some non-France French dialects that count normally.

The Spanish might talk too fast to understand anyway, though.

French is the only Romance language that does the count-by-twenties thing, as far as I know, but apparently some of the Celtic languages do it too. So French may have picked it up from Breton (or Gaulish or who-knows).