Use the Alphabet Coding Method $$( A = 1 , B = 2 , C = 3 , \ldots Z = 26 )$$

Essay

Use the alphabet coding method $$( A = 1 , B = 2 , C = 3 , \ldots Z = 26 )$$ to solve the problem.
-The function defined by $f ( x ) = x + 2$ was used to encode a message as: $\begin{array} { l l l l l l l l l l } 15 & 3 & 22 & 10 & 9 & 7 & 16 & 11 & 23 & 21 \end{array}$ Find the inverse function and determine the message.