Answer
$M=\begin{bmatrix}31&42&18\\22&25&11\end{bmatrix},\text{ }J=\begin{bmatrix}25&36&12\\38&32&15\end{bmatrix}$
Work Step by Step
We build the matrix $M$ for the sales in May: the number of lines would be $2$ (one for the downtown, one for the mall) and the number of columns would be $3$ (one for each model):
$$M=\begin{bmatrix}31&42&18\\22&25&11\end{bmatrix}.$$
We build the matrix $J$ for the sales in June in the same way as we built matrix $M$:
$$J=\begin{bmatrix}25&36&12\\38&32&15\end{bmatrix}.$$
