I wrote a (very long) blog post about those viral math problems and am looking for feedback, especially from people who are not convinced that the problem is ambiguous.
It's about a 30min read so thank you in advance if you really take the time to read it, but I think it's worth it if you joined such discussions in the past, but I'm probably biased because I wrote it :)
That's the correct answer if you follow one of the conventions. There are actually two conflicting but equally valid conventions. The blog explains the full story but this math problem is really ambiguous.
...the rules of Maths.
I read it. And I'm not a mathematician, so the answer is 9.
E: The salty mathematicians down-voting this can get fucked lmfao
Ooh now I get you, sry. True. But sadly you now know the truth and you have to be careful with the implicit multiplications on your tax forms from now on ;-)