Don't lament those Facebook questions too much. Sure, it's funny how many people get them wrong, but they are also intentionally misleading, if strictly speaking, mathematically accurate. That multiply by 0 makes people get all excited, because they remember that multiply anything by 0, and you get a 0. And so they answer, thinking they discovered the, "Trick". It's not a problem you would have in a real math problem with parenthesis all over the place very often, and almost never in basic, everyday applied use of the math fundamentals. So people are bad at math, sure, but those questions exaggerate the problem.