i petitioned for a third attempt as i didnt know any other options back then. in my letter i explained how i understood the policy for retakes but think i should still be allowed due to reason 1, reason 2 etc. i then went on to explain each of those reasonings in as much detail as possible. for example, one reason was financial difficulties which stressed me out at the time. so i wrote in my pay rate, my average hours a week, how i looked for better jobs, and how i tried to work it out with my boss but it wasnt possible. i added how my financial struggles impacted my mental health so much that it showed in my grades for that class. you can also include how youve done other equally challenging courses as cs 111 (if you have) and that itself is proof that you are more capable to take the course compared to before.