The third sentence is good. Here are some examples of when you'd use "abound": https://learnersdictionary.com/definition/abound

Hi, Your third sentence, exam is full of mistakes, is what we would say. The term abound is quite theatrical, academic, and not really daily speech From what your trying to say I’d write / say: I had so many mistakes in my math exam I made so many mistakes in my math exam My math exam was full of mistakes (could mean something different, like the questions in your math exam had mistakes in them!!) So, who is making the mistake? The professor writing a mistaken exam or you writing wrong solutions in your exam Happy for you to write back with any questions

Thanks, Hollee H.

Hi 👋. Native English speaker here. I rarely say or hear the words “abounds in” or “abounds with”. Most people would say “my math exam is /was (depending on present or past tense) full of mistakes”. Hope this helps!