Answer
If $A=\left[ \begin{matrix}
1 & 2 & 3 \\
\end{matrix} \right]$, then the order of the matrix is $1\times 3$.
Work Step by Step
Note that if $A$ is the matrix of size $m\times n$, then the order of the matrix $A$ is $mn$.
Consider the matrix, $A=\left[ \begin{matrix}
2 & 3 & 7 \\
\end{matrix} \right]$
This matrix has one row and three columns.
Therefore, the order of this matrix is $1\times 3$.
