Hess' Law help

I'm really confused about Hess' law. I thought I got it, but I thought I'd go over the section in the revision guide and do the questions and I didn't get any right. I am now really confused as my class notes seem to contradict the revision guide.Please can someone explain it to me possibly with a worked example.

I'm really confused about Hess' law. I thought I got it, but I thought I'd go over the section in the revision guide and do the questions and I didn't get any right. I am now really confused as my class notes seem to contradict the revision guide.Please can someone explain it to me possibly with a worked example.

Think I have sorted it now but any help would still be useful

The main concept youve gotta grasp is whether you do a subtraction or addition, although Im still a bit unsure about it all. You have to really understand what youre actually doing with them, so the best place to learn Hess Law is probably
http://chemrevise.org/revision-guides/ just chose the topic, Goalby notes is definetley the best way to get a good grade in Chem.

Read through this interactive guide to Hess' law