$$ \begin{bmatrix} 10&-13 \\ -8&11 \end{bmatrix}-\begin{bmatrix} -9&-17 \\ -8&14 \end{bmatrix}=\begin{bmatrix} 10-(-9)&-13-(-17) \\ -8-(-8)&11-14 \end{bmatrix} $$ $$ =\begin{bmatrix} 19&4 \\ 0&-3 \end{bmatrix} $$