Solution:
The given example states that:
- A = 1
 - ⇒ A = The first letter of the alphabet
 
Now, let's decode the number code.
Decoding the number code:
- 6 = sixth letter of the alphabet = F
 - 18 = eighteenth letter of the alphabet = R
 - 5 = fifth letter of the alphabet = E
 - 5 = fifth letter of the alphabet = E
 - 17 = seventeenth letter of the alphabet = Q
 - 16 = sixteenth letter of the alphabet = P
 - 9 = ninth letter of the alphabet = I
 - 15 = fifteenth letter of the alphabet = O
 - 21 = twenty-first letter of the alphabet = U
 - 20 = twentieth letter of the alphabet = T
 
Coded word: F R E E Q P I O U T ⇒ Freeqpiout