Ah, so in your world, a teacher of something is never, ever allowed to make a simple mistake in that area? Nice world you live in, I hope you satisfy your own standards when you become a professional.

Sad truth of life, I'm an electrical engineer and I prefer an impossible integral over a simple 2-digit arithmetic...

Maybe he just doesn't like you cause your a smart a@@

Not all teachers have a degree in the subjects they teach. It's how school districts cut costs so the education of growing minds will be more economically efficient. There is nothing like discount academics.

is it possible that she didn't grade your paper? Teachers sometimes have student aides helping them with things like that

Many teachers outsource such things to senior students. Hope you got this sorted out.

Honestly, while this isn't great, try and picture the position I was in last week. I was marking 120 exam papers for my year 11s. In one day I did 12 hours of marking. We've been going over them, and, yup, there's a few mistakes in the mark totals. I understand you find this frustrating, and perhaps your teacher is just awful, but do spare a thought for the sheer volume of marking many teachers have to do and ask yourself; isn't the occasional brainfart understandable. However, hope the teacher apologised and fixed it, I know I would.

Or maybe she didn't count those marks because you failed horribly

Have you ever considered that your math teacher probably teaches more than just YOU and probably had about 150 tests to grade and add up? This doesn't make him/her bad at math- it makes them a teacher who works 7 days a week to do the best they can for you. Mistakes happen. Stop feeling so smug. (Sorry, I'M a teacher)

Even teachers make mistakes