As Rod said, An Addendum contains add-on information, explanations, definitions, expansion of concepts, and so on.
You could also check out the other posts on the web site here about inequality problems.
Go to the top of the page, where it says, “Questions HOT! Unanswered Tags Users Ask a Question” and click on Tags. Now search for the Tag “inequalities” – use Ctl-F. You should find it in the left hand column.
Read through some of those. They may give you some help. Then post your own problems on inequalities and we can explain things to you.