Chapter 3 Linear Systems and Matrices - 3.8 Use Inverse Matrices to Solve Linear Systems - 3.8 Exercises - Skill Practice - Page 214: 13

$$X=\begin{pmatrix}11&9\\ -9&-6\end{pmatrix}$$

Isolating X by taking the inverse of the matrix, we find: $$\begin{pmatrix}1&1\\ 4&5\end{pmatrix}X=\begin{pmatrix}2&3\\ -1&6\end{pmatrix} \\ X=\begin{pmatrix}1&1\\ 4&5\end{pmatrix}^{-1}\begin{pmatrix}2&3\\ -1&6\end{pmatrix} \\ X=\begin{pmatrix}11&9\\ -9&-6\end{pmatrix}$$