Will you guys help me with my algebra homework today?

This one problem is just kicking my butt. It’s an on-line course, and when I ask the instructor for help, whenever she gets around to replying she sends back a message that’s basically a duplicate of what I get when I click the help tab on the lesson. I have to have this last unit done today, as well as a chapter test. It’s all due tomorrow morning at 8:00 a.m.

Here is the problem:

x – (1.8x – 4(x-3.1(x+11)))=0 (don’t fuss over the parenthesis signs..)
I get this far
x – (1.8 – 4(x – 3.1x – 34.1))=0
x – (1.8 – 4x – 45.7x + 136.4)=0
x – (1.8x) – (4x) – (12.4x) – (136.4)
Following is where I get confused because the signs change at random, or so it seems to me. I just need some sort of trick to memorize that will allow me to start flipping signs around as needed. The example shows that the next step is:
x-1.8x + 4x - 12.4x – 136.4 = 0.
Please explain how x – (- 4x) turns into + 4x, whereas x- (-12.4x) says with the – sign…....
Also, to me, the explanations get all long a drawn out and there always seems to be one step that is a little redundant. In this case I think I can get by without the “x – (1.8x) – (4x) – (12.4x) – (136.4)” step….if I can puzzle out why the signs change.

I have such a headache.

Lol! I went to preview the question and every thing was crossed out ! :)