I don't get how these matrices are solved

$A= \begin{bmatrix} 4&2& 0\\ 2&-4&8 \end{bmatrix}$

$B= \begin{bmatrix} -15\\ -3\\ -9 \end{bmatrix}$

$C=\begin{bmatrix} 1 && 2 \\ 3 && -3\\ -2&&-1 \end{bmatrix}$

Given the following information how is this solved?

$CA /2$