I have been reading these slides about Hill cipher.
And there it says that the value of K is the following:
\begin{equation} K= \begin{pmatrix} 11&8\\3&7 \end{pmatrix} \end{equation}
Now I need to calculate $K^{-1}$, so for that reason I calculate the adjoint matrix by using the cofactors. For what I know it should be:
\begin{pmatrix} 7&-3\\-8&11 \end{pmatrix}
but in the slides it appears that is:
\begin{pmatrix} 7&-8\\-3&11 \end{pmatrix}
which is different from the one I calculate, what am I doing wrong?