Hello there!
Your correct answer will be the last one.
I'll show you why.
So, in your little x-y graph, you have these numbers. If able to, I will almost always use the row with a value of +/- 1 in it.
Next, you put these numbers as your coefficients for x and y.
3y = -1x
After this step, just divide to get y with a coefficient of 1.
3÷3y = 3÷ -1x
This, then equals y = -1/3x
I hope this helps a bit!
Brady