Use the Alphabet Coding Method (A =1, B = 2

Short Answer

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