The equation isn’t ambiguous at all. If it was supposed to have an answer other than “9,” the person who wrote it down was an idiot who needs to take remedial math and figure out how to use parenthesis correctly.
What’s the point of developing any sort of syntax or notation to express math if we go back and say “weeeellll… maybe they actually meant something other than what they actually wrote! Maybe they intended to add another set of parenthesis! Maybe, instead of a ‘6,’ they meant to write ‘8,452’!”
I’m all for creative thinking, but if I interviewed someone who said that this equation was “ambiguous,” they wouldn’t get the job due to the fact that they’re blatantly, unambiguously, wrong.