Rotate vector around axis, so that it falls onto plane spanned by rotation axis and second vector

Question

I have a vector $v$, a rotation axis $r$, and a second vector $x$. The rotation axis $r$ and the vector $x$ are spanning a plane. I want to rotate $v$ around $r$ so that it falls onto the plane spanned by $r$ and $x$. I am not quite sure how to do this the best.