a) Modus Tollens (or whatever you call it on your course), that is:
which you need to apply twice.
b) One of De Morgan's laws:
c) One application of what you seem to call IR above.
See how you get on with that, and come back if you still can't master it. Worry not, it took me ages to get the hang of this. Then, as you say, it's like snowboarding (or in my case it was waterskiing).