Explanation:
The given matrix appears to be
[tex]X = \begin{bmatrix}0 & 2 & 4 & 61\\0 & 3 & 6 & 9\\0 & 4 & 8 & 12\\\end{bmatrix}[/tex]
Though I think there might be a typo and that 61 should be 6 instead. However, it won't affect the final answer.
The notation [tex]X_{2,4}[/tex] means we look at the element in row 2, column 4 of this given matrix. That would be the 9 at the very end of the second row.
So we can say [tex]X_{2,4} = \boldsymbol{9}[/tex]
