I have a test tomorrow and I'm not getting the answers on a study guide for a couple and I forgot how I did another and lost all my understanding.

These are the formulas I was given:http://i.imgur.com/6rwL0S6.jpg

This is #4(which I got close to the answer but not the entire thing): http://i.imgur.com/NaJhF5Y.jpg

My work: http://i.imgur.com/l8OHuCD.jpg

This is #9(where again I got close to the answer but it's not negative): http://i.imgur.com/irn4fUd.jpg

My work: http://i.imgur.com/VGdxQkx.jpg

This is #11(which I've done before but looking at it again I'm very confused and have no understanding of my work. It'd be nice if someone could show me this one step by step): http://i.imgur.com/8RKTBfe.jpg

My work: http://i.imgur.com/nexHgNv.jpg

These are the answers:http://i.imgur.com/qXXNP0j.jpg

Thanks in advance.