**Toolbox:**

- Order of matrix=A matrix having m rows and n column is called matrix of order $m\times n$ or simply $m\times n.$
- Number of elements in a matrix=Product of rows and columns in a matrix.
- i.e $m\times n.$
- m=rows,n=column.
- Elements of matrix:$a_ij$
- It is element lying in the $i^{th}$ row and $j^{th}$ column.

In the given matrix we have 3 rows and 4 column.

Order of matrix is $3\times 4.$

Element of matrix=row $\times$ column.

In the above matrix we have 3 rows and 4 columns

Number of elements=$3\times 4$

$\qquad\qquad\qquad\;\;\;=12.$

The element $a_{13}$

$a_{13}\rightarrow$ $1^{st}$ row and $3^{rd}$ column \[a_{13}=19.\]

$a_{21}\rightarrow$ $2^{nd}$ row and $1^{st}$ column \[a_{21}=35.\]

$a_{33}\rightarrow$ $3^{rd}$ row and $3^{rd}$ column \[a_{33}=-5.\]

$a_{24}\rightarrow$ $2^{nd}$ row and $4^{th}$ column \[a_{24}=12.\]

$a_{23}\rightarrow$ $2^{nd}$ row and $3^{rd}$ column \[a_{23}=\frac{5}{2}.\]