Chapter 6, Matrices and Determinants - Section 6.3 - Inverses of Matrices and Matrix Equations - 6.3 Exercises - Page 523: 30

$\left[\begin{array}{c c} 5/6& 1 & 1/6&-1/6\\ -1& -1&0&0\\ -4/3& -1&1/3&2/3\\13/6&2&5/6&1/6\end{array} \right]$

Using a graphing calculator (see attached picture), we get the inverse matrix: $\left[\begin{array}{c c} 5/6& 1 & 1/6&-1/6\\ -1& -1&0&0\\ -4/3& -1&1/3&2/3\\13/6&2&5/6&1/6\end{array} \right]$