### Instruction: Find the focus of the parabola $x = -\frac{1}{12} y^2.$.### Response: I know that a parabola of the form $x = \frac{1}{4p} y^2$ has a focus at $(p, 0)$, where $p$ is the distance from the vertex to the focus.
So, I can compare the given equation to this standard form and see that $\frac{1}{4p} = -\frac{1}{12}.$
This means that $p = -3$, so the focus is at $(-3, 0).$