I dont understand 5 exercises besides those two,

I had done the second exercise yesterday with teh technique of the first one, it wasnt that I did it wrong but I wrote it wrong in my Homework, if you hadn't written it I wouldn't have noticed.

Also there was a protest at the University so now I have 2 days to finish my homework.

5 other exercises that I don't know how to do:

a)solving for x:

a-2[b-3(c-x)]=6

b) I did an exercise and I got:

0≥x≤-2

how do I write it in the <------------------------->

and in the interval notation

c)How do I find the two answers to:

3-|2x+4| ≤ 1

I have read and tried following what my book said and I can't get the answers that appear in the book.