I am confused on this. Can anyone show me where to start on how to solve it?

Given the cipher and function below, decode the following message:

14-2-21-9 10-20 7-22-15

Function: f(x)=2x-2

Cipher

A=2, b=4, c=6, d=8, e=10, f=12, g=14, h=16, i=18

j=20, k=22, l=24, m=26, n=28, o=30, p=32, q=34

r=36. S=38, t=40, u=42, v=44, w=46, x=48, y=50, z=52

Hint: Plug each number into the function and then use the cipher to convert the output to the coded letter.

2 answers

f(14) = 2*14-2 = 26
26 = m
so the first letter is m

and so on
Thank you