Yes, there is no ambiguity if you (always) do your calculation from "left to right".

There is also no ambiguity if you always do multiplication before division.

You join the "9-people" because left to right has no ambiguity, but the other side has no ambiguity either.

The ambiguity arises when we have these two different rules or orders of operation and haven't agreed on which one we are going to use. It is 'ambiguous' because the writer of the expression could have meant two things and we have no way of knowing which one she/he meant.

So basically you have chosen your side arbitrarily like everyone else, unlike the actual mathematicians who had the correct answer by saying it's unclear or ambiguous.