$\text{Let M be a 3X3 matrix satisfying M }\left[\begin{array}{l}\text{0}\\ \text{1}\\ \text{0}\end{array}\right]=\left[\begin{array}{l}-1\\ 2\\ 3\end{array}\right],\text{ M}\left[\begin{array}{l}\text{ 1}\\ \text{-1}\\ \text{ 0}\end{array}\right]=\left[\begin{array}{l}1\\ 1\\ -1\end{array}\right]\text{ and M}\left[\begin{array}{l}\text{1}\\ \text{1}\\ \text{1}\end{array}\right]=\left[\begin{array}{l}0\\ 0\\ 12\end{array}\right]$ $\text{Then the sum of diagonal entries of M is }\mathrm{.........}$

$\text{M=}\left[\begin{array}{l}\text{a b c}\\ \text{d e f}\\ \text{g h i}\end{array}\right]$

$M\left[\begin{array}{l}\text{0}\\ \text{1}\\ \text{0}\end{array}\right]=\left[\begin{array}{l}-1\\ \text{ 2}\\ \text{ 3}\end{array}\right]\text{ b=-1,e=2,h=3}$

$\text{M}\left[\begin{array}{l}\text{ 1}\\ \text{-1}\\ \text{ 0}\end{array}\right]=\left[\begin{array}{l}1\\ \text{ 1}\\ \text{-1}\end{array}\right]\text{ a=0,d=3,g=2}$

$\text{M}\left[\begin{array}{l}\text{1}\\ \text{1}\\ \text{1}\end{array}\right]=\left[\begin{array}{l}\text{ 0}\\ \text{ 0}\\ \text{12}\end{array}\right]\text{ g+h+i=12, i=7}$

$\text{Sum of diagonals = 9}$