Answer:
I don't believe there is an answer to this.
Explanation:
How it would usually go is you find the square root of both sides when it is simplified to this point. However, as -9 is negative, it has no square root.
If -9 were positive, however, the square root would be 3 and the question would look like this:
v = 3
Thus, your answer would be 3.
However, they may have given you a way to do this, so this is only what I think based off the experience I have atm.