Answer
$M_{23}=0$
and
$A_{23}=0$
Work Step by Step
The minor of an element is defined $a_{ij}$of a determinant is defined as the determinant obtained by deleting its ith row and jth columns and the minor $M$ of an element $a_{ij}$ is abbreviated as $M_{ij}$.
Further, the cofactor of an element $a_{ij}$ is abbreviated as $A_{ij}$.
where $A_{ij}=(-1)^{i+j} M$
Here, $M_{23}=\begin{vmatrix}1&0\\0&0\end{vmatrix}=0$
and
$A_{23}=(-1)^{2+3} M_{23}=(-1)(0)=0$