I have referred to Sourabh Ranka's Solution for this question
==How can bob decrypt the message?== Bob knows the secret matrix. He can decrypt the message. He needs to multipy the inverse of the secret matrix with the first 3 entries then the next 3 and so on. By this he will obtain the decrypted message.
Can Eve decrypt the message without finding the inverse of the secret matrix?
Eve should know the inverse of the matrix to decrypt the message.(Reason is explained on top)
Therefore, on solving we find the inverse of the secret matrix to be
$ \begin{matrix} - \frac{2}{3} & 0 & \frac{2}{3} \\ 0 & 1 & 0 \\ 4 &0 & -1 \end{matrix} $
What is the decrypted message corresponding to (2,23,3)?
the decrypted message corresponding to (2,23,3) is in the order of the alphabets. Professor had done something similar to this in the first class. So 2,23,3 are B ,W, E respectively.
$ (2,23,3) \to \begin{matrix} - \frac{2}{3} & 0 & \frac{2}{3} \\ 0 & 1 & 0 \\ 4 &0 & -1 \end{matrix} \to BWE $
