How do you evaluate a matrix.

Step 1: Matrix
Then we need evaluate a matrix, it must be a square matrix of order $n\times n$. it can be $2\times 2,3\times 3,4\times 4$
For eg:
$\left(a,b,c,d\right)2\times 2$ is a square matrix of order $2\times 2$
$\left(a,b,c,d,e,f,g,h,i\right)3\times 3$is a square matrix of order $3\times 3$
Step 2: Evaluating a matrix
$A=\left(a,b,c,d\right)2\times 2$we can evaluate the $2\times 2$ matrix by multiplying the and then subtracting it
$\left(A\right)=\left(ad-bc\right)$
For $3\times 3matrix$

Hide row and column along which we evaluating the matrix
Then the remaining element is $\left(e,f,h,i\right)then\left(A\right)=\left(e,i,-,f,h\right)$in this we evaluate the matrix along element $a$.
Similarly, if we evaluate the matrix along element $b$ then $\left(A\right)=\left(d,f,g,i\right)then\left(A\right)=\left(d,i,-,g,f\right)$
Hence, in this way we can evaluate a square matrix .