Calculation of inverse matrices

Calculation of the inverse matrix A-1 of the second order
|a11 a12|
A= |a21 a22|

|a11: a12: |
|a21: a22: |





Calculation of the inverse matrix A -1 of the third order
|a11 a12 a13|
A= |a21 a22 a23|
|a31 a32 a33|

|a11: a12: a13: |
|a21: a22: a23: |
|a31: a32: a33: |