So basically, what you want to do, is just add or subtract everything together.
Think of -9 as a number 9 to the left of a number line, and then you're adding 11 units, moving -9 11 times to the right. Once you do this, you get 2. Now, adding negative 9 is the same thing as moving 2 9 times to the right. Once you do that as well, you'll get -7. And then just move -7 12 units to the right on the number line and you'll get 5.
Haha that was a really bad explanation, but hope I helped!
