* x+30=-3-2x
<=> x + 2x = -3 -30
<=> 3x = -33
<=> x = -11
* [x+5]+[x-9]=x+2
<=> x + 5 + x - 9 = x + 2
<=> x + x - x = 2 - 5 + 9
<=> x = 6
* [27-x]-[15-x]=x-24
<=> 27 - x - 15 + x = x - 24
<=> - x + x - x = -24 - 27 + 15
<=> - x = - 36 <=> x = 36
* 5x-[-24]=3+2x
<=> 5x + 24 = 3 + 2x
<=> 5x - 2x = 3 -24
<=> 3x = -21
<=> x = -7
* 22-[2-3x]=12-4x
<=> 22 -2 + 3x = 12 - 4x
<=> 3x + 4x = 12 - 22 + 2
<=> 7x = -8
<=> x = -8/7