Let me preface this by saying yes I have read the rules, yes this is technically a homework question, but I'm not directly asking for the answer. I've been reteaching myself math, but for some reason I cannot grasp the concept of Interval Notation.

Ultimately yes, I am looking for the answer, but I mainly just need assistance into understanding this. The teacher didn't proved the modules for this, so I'm having a really hard time trying to understand this. Sorry in advance.