As you can see, the line below says 8x+12=-20. This is perfectly fine. Though when she gets rid of 12, she adds twelve. So if she did, it would look like 8x+24=-8. No, she made it 8x=-8. When getting rid of something, you must do it's value's opposite. Therefore, it would be 8x=-32. Since subtracting negative by negative is negative.
