I can't seem to finish this problem. I'm fine until the combining like terms on each side. Is there a set of rules like if one of the terms is on the opposite side of the = then you subtract?? There doesn't seem to be a pattern to follow to get the right answer:

-7(y+1) =4y-6+2(2y+4)

-7y-7+4y-6+4y+8

-7y-7=8y+2

-7y=8y+9

I get all of this so far. Here is where I have trouble. Is there a set pattern to this? Because I never seem to get the write answer using the same formula:

-15y=9 I guess it's -7y+8Y and you get -15? How is that? If I add -7+8 I get 1 not -15. It looks like it's just 7+8 but how does it stay negative and how do I know that when solving? Example, what if it was 7y= -8Y? Would it still be -15? SO frustrating! I get everything but this part.