Chapter 2 - Matrices - Review Exercises - Page 98: 15

$$ \left[ \begin {array}{cccccc} 1&-1\\ 2&-3\end {array} \right].$$

Since $ad-bc=(3)(-1)-(-1)(2)=-1\neq 0$, then the matrix has inverse given by $$ - \left[ \begin {array}{cccccc} -1&1\\ -2&3\end {array} \right]=\left[ \begin {array}{cccccc} 1&-1\\ 2&-3\end {array} \right].$$