... ; For #19, same thing. Just bruteforce and test out the answer ... panic when I need to bruteforce a question... I always think ... knowing when you need to bruteforce. It's rare you have ...
I don't know how much this will help, but when I had the same problem I had to bruteforce myself to stay focused and study. However, it could be a sign of burn out, maybe take 2 or 3 days off and relax a bit?