I need help which letter is it?

Answer:
B
Step-by-step explanation:
1. So your original equation is -y+2y-9=1. The first step is to isolate your variables so put 9 on the otherside.This gives you -y+2y=10.
2. Now you can combine like terms, 2y-y=y. This gives you y=10.
3. Now just look at your answer choices that when solved gives you y=10