, cheong wrote

*snip*

I don't have problem for people getting it wrong, but have problem where the teachers teach it without explaining the fundamential reason of doing so.

Once you know the reason, even if you forgot the order, you can deduce it correctly yourself. It's all related to converting goods to their monetary value. "M"oney is the basis of ancient "M"athematics.

The problem is that operator precedence is largely a convention; there's no real reason why 3 + 3 * 4 = 15 and not 24; it's just that we decided it has to be that way.

That's what makes it hard to teach: you can paraphrase it all you want, but the answer is essentially "just because" and that never flies too well with kids.