Answer:
4
Explanation:
1. Substitute the x value of -9 into the equation:
6(-9) + 9y = -18
2. Simplify
-54+9y = -18
3. Add 54 to both sides to get 9y by itself, the goal is to get y by itself
9y = 36
4. Divide by 9 on both sides to get y completely by itself
y = 4