Algebra Help

[orgekas]

I didn't know where to post this and it's actually a uni maths question.
The questions are on the attachment. I kinda worked out the answers but I can't  understand all of them.

Please help me.

If you cant see the attachments please tell me
Question 4 continues as follows:
State if Z3 is a field.
If it is state the additive and the multiplicative inverses for each element.
If it's not state which field laws are not satisfied

[keltingmeith]

Don't worry, I've fixed its placement for you. (Y) I can't help more though, sorry - algebra is scary. (although I might have a go after I've finally watched this stats lecture I'm behind on...)