Answer
(a.) Size $=3\times 4$.
(b.) Element $=5$
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
$\begin{bmatrix}
9& -3&7&1\\
0 & -2& 6 & -3\\
1 & 1 & 5 & -4
\end{bmatrix}$
Number of rows $=3$.
and number of columns $=4$.
Hence, the size of the matrix is $3\times 4$.
(b.)
$(3,3)$ is a position at row $3$, column $3$.
The element at row $3$, column $3$ is $5$.
Hence, the element is $5$
