Well, I'm not exactly a "parent" but certainly I try to "educate" her about things I lived. (since we both live together and alone since young (18)).
The fact is that she is 22, and is at a pre-university class that she has to pass in order to be able to start studying the career she chose.
We went to high school together at a public school and the level wasn't very good, I helped her in exams and she helped me doing the group projects while I was sleeping (I was working at night in that time).
She got depressed because she failed in a very simple math exam, where, for example, she had to find if a candidate with 11000 votes out of 49000 had more than 25% of the votes.
I told her that I will be there for her even if she doesn't pass the course (She keeps saying that I will leave her because of her intellectual level), and that we all will still be there.
I keep telling her that I failed twice trying to enter a university (the level was much higher, but I still failed) to make her feel better.
How can I make her pass this situation and how can I prepare her to better understand problems to solve? I need to motivate her so she doesn't quit and keep trying besides the fails.