$65$

$\left(\begin{matrix}4&1&2\\3&10&1\\5&6&4\end{matrix}\right)$

$\left(\begin{matrix}\frac{34}{65}&\frac{8}{65}&-\frac{19}{65}\\-\frac{7}{65}&\frac{6}{65}&\frac{2}{65}\\-\frac{32}{65}&-\frac{19}{65}&\frac{37}{65}\end{matrix}\right)$

$18$

$\left(\begin{matrix}4&3&5\\1&10&6\\2&1&4\end{matrix}\right)$

$3,3$

$\left(\begin{matrix}1&0&0\\0&1&0\\0&0&1\end{matrix}\right)$

$\left[\begin{array}{rrr}34 & 8 & -19 \\ -7 & 6 & 2 \\ -32 & -19 & 37\end{array}\right]$