I'm not entirely sure how to go about answering these questions. for 6a, I think it can be explained through a theorem, something about the number of rows and variables
But for the rest, I'm not actually sure what is being asked. This section of my course has posed the most difficulty for me, because I have no access to lectures (extramural student), and there was literally only a page of explanation followed by about 40 questions. I've been through all the Khan Academy stuff, but I don't really get what is being asked here. Any tips on how to proceed? I can do all the row reduction and basic row operations, but how should I go about using them?