Far too much of mathematics involves annoying competing notational standards. Most of the time, it's just there's four ways of writing the same thing, some favoured by mathematicians, some by physicists, some by computer scientists and so on. But sometimes, you get discrepancies with things like log/lb/lg/ln, or other things (such as using the same letter to refer to two different things, and other more major ones that don't come to mind right now).
There's also the public understanding of the BIDMAS rule (You might use PIDMAS in the US, I guess, since you call parentheses what we call brackets), which people regularly get wrong (although the ambiguity could be removed easily using brackets). For example, what does 5-3+2 equal?
If you said 0 then you've fallen into the regular trap. The answer is actually 4. This is because the rule really means (B)(I)(DM)(AS), evaluating things in each bracket in the order they come, not explicitly addition before subtraction.