, Charles wrote

It's not necessarily about getting it right. When you get something wrong you inevitably learn why. Then, you acquire new knowledge that stays with you. 

All of us would get each of the examples in this thread wrong at some point in time -> the points in time when we didn't know anything about order precedence of mathematical operations.

Here's to ignorance and the pursuit of knowledge. You can't have one without the other.

C

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.