Why do I disagree with my calculator? I followed the order of opperations but my answer disagrees with my calulator's.

Problem: $331.91 - 1.03 - 19.90 + 150.00$
Calculator answer: $460.98$
My answer: $162.98$

Why the discrepancy?

The calculator is correct of course (at least in magnitude of the answer, I haven't actually calculate it, and I won't). I bet you are having problems with those negative terms. 
For this particular exercise and infinite more like this one, you can take another approach, more intuitive than just following rules like a robot. Look at what you are being asked: it's a sum. A sum with negative and positive numbers. We can already see that the positive numbers exceed in magnitude the negative ones, so there is no way in hell that your answer is correct. 
Structurally you could add all positives, add all negatives and then add those two groups, just like you can identify the 'subject' and 'predicate' part in a grammatical sentence. In my experience, that has always minimize sign-related errors.
