Thank you for using the site. I'll be happy to help you with this problem set. Can you post all of the questions in a Word document or PDF?
Just in case there is any confusion, I can't answer the first five questions about the relative frequencies, or the frequency for the 5.0 - 5.9 class, without knowing the total number of observations. If you can send that number in your reply, I'll be able to get these answers to you.