First, you move the -15 to the other side along with -9 so you have like terms in the same side. This will make it easier for you to solve for the answer.
To move -15 to the other side, you simply move it over next to -9 and change the sign. Since it was -15, it becomes positive 15. So the equation should look like n= -9 + 15.
Now, the equation looks much easier, right? All you need to do to find the answer is do -9+15, which equals 6. That's it!
