We Have Encoded a Message by Assigning the Numbers 1

Short Answer

We have encoded a message by assigning the numbers 1 - 26 to the letters a - z of the alphabet, respectively, and
assigning 27 to a blank space. We have further encoded it by using an encoding matrix. Decode this message by finding
the inverse of the encoding matrix and multiplying it times the coded message.
-The encoding matrix i $$A = \left[ \begin{array} { r r r } 1 & 0 & 0 \\- 1 & 1 & 0 \\1 & 1 & 1\end{array} \right] \text { and the encoded message is } 9,11,56,9,10,55,12 , - 3,43,9,5,30$$