Question

Combining like terms... 12r-8-12. = -8r is this correct

Answer 1

When combining like terms you just combine numbers with the same variables.
For example:
2r+3r-7+1
If I combine like terms I get
2r+3r=5r
and -7+1=-6
So you get 5r-6

Answer 2

So since you have 12r-8-12
You have just 12r
then -8-12=-20
So you get 12r-20

Answer 3

Understand it now?

Answer 4

yes

Answer 5

thanks a lot!