Answer
(a.) $2\times 2$ matrix.
(b.) $0$ is in the $(2,1)$ position.
Work Step by Step
(a.)
The size of the matrix is equal to number of rows multiply by number of columns.
The given matrix is
$\begin{bmatrix}
5& 9\\
0 & -3
\end{bmatrix}$
Number of rows $=2$.
and number of columns $=2$.
Hence, the size of the matrix is $2\times 2$.
(b.)
$(2,1)$ is a position at row $2$, column $1$.
The element at row $2$, column $1$ is $0$.
Hence, the element is $0$
