Linear combinations

If u=[523]\vec{u}=\begin{bmatrix}5\\-2\\3\end{bmatrix}is a linear combination of v=[2k3]\vec{v}=\begin{bmatrix}-2\\k\\3\end{bmatrix}and w=[321]\vec{w}=\begin{bmatrix}3\\2\\-1\end{bmatrix}, what is the value of kk?

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