Vector Spaces & Bases · Hard problem

The vector $\mathbf w = (-6, -4, 0)$ lies in the span of $\mathbf u = (3, -3, 3)$ and $\mathbf v = (3, 2, 0)$. Find the scalars $a, b$ with $\mathbf w = a\mathbf u + b\mathbf v$.