1+1

A = {{5,6,2,3},{-12,10,19,-20},{2,14,18,-5},{4,2,7,1}};

Det[A]

B={{2},{7},{2},{5}};

Inverse[A].B//MatrixForm

A2B = A;
A2B[[All,2]]=Flatten[B];

A2B//MatrixForm

A2B[[All,2]]=B;

A2B//MatrixForm

B

Flatten[B]

Flatten[A]

A2B[[All,2]]=Flatten[B];

A2B//MatrixForm

A2B[[2,4]]

A2B[[All,4]]

A2B[[2,All]]

Det[A2B]/Det[A]