Need Help with:

a)solving for x:

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

b)how do I write

0≥x≤-2

in the <------------------------->

and in 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.

d)Is this correct:

solving for m:

$\displaystyle

F= G \frac {mM} {r^2}

$

$\displaystyle

m = \frac {Fr^2} {GM}

$