Answer
${{a}_{34}}$ denotes the element in the third row and the fourth column of the matrix.
Work Step by Step
A matrix $A$ is denoted by the expression, $A=\left[ {{a}_{ij}} \right]$
Here, ${{a}_{ij}}$ represents the general element of the matrix $A$ which lies in the ${{i}^{\text{th}}}$ row and ${{j}^{\text{th}}}$ column. Therefore, the notation ${{a}_{34}}$ stands for the element presents in the third row and fourth column.
