This isn’t grade 11 math. It’s grade 8 math.
Well, maybe it’s grade 11 math in a school of imbeciles and idiots.
This is really hard, so I’ll do it for you.
9 + 3g = 12g
9 = 12g - 3g
9 = 9g
1 = g
You might need “g,” but what you really need is a brain.
It may be in your grade 11 book, but that question is grade 8 or 9.
It may be your teacher is a passive aggressive bi tch. She may have become that way after years of trying to teach on grade level to students who have not learned the prerequisites.
Many web sites teach basic high school math. PurpleMath is one and there are many others. If you spend an hour a day on these sites, you will learn this and be on grade level (or beyond it) in few weeks. If you have a question, you can present it on here. You will get a serious answer (without the sarcasm).