## Question

In the expression $$2\begin{bmatrix} -1 & 0\\ 2 & -2\end{bmatrix} -\begin{bmatrix} 1 & 2 \\ 4 & 3\end{bmatrix} = \begin{bmatrix} -3 & a \\ 0 & b\end{bmatrix}$$, what is $$a - b$$?