[Exercise Sync] Docs and Metadata for Affine-Cipher & Alphametics. (#3721)

* Synced docs for Affine-Cipher and Alphametics.

* Alphametics metadata file.

exercises/practice/affine-cipher/.docs/instructions.md

@@ -18,10 +18,10 @@ E(x) = (ai + b) mod m
 
 Where:
 
-- `i` is the letter's index from `0` to the length of the alphabet - 1
+- `i` is the letter's index from `0` to the length of the alphabet - 1.
 - `m` is the length of the alphabet.
   For the Roman alphabet `m` is `26`.
-- `a` and `b` are integers which make the encryption key
+- `a` and `b` are integers which make up the encryption key.
 
 Values `a` and `m` must be _coprime_ (or, _relatively prime_) for automatic decryption to succeed, i.e., they have number `1` as their only common factor (more information can be found in the [Wikipedia article about coprime integers][coprime-integers]).
 In case `a` is not coprime to `m`, your program should indicate that this is an error.

exercises/practice/alphametics/.docs/instructions.md

@@ -1,6 +1,6 @@
 # Instructions
 
-Write a function to solve alphametics puzzles.
+Given an alphametics puzzle, find the correct solution.
 
 [Alphametics][alphametics] is a puzzle where letters in words are replaced with numbers.
 
@@ -26,6 +26,4 @@ This is correct because every letter is replaced by a different number and the w
 
 Each letter must represent a different digit, and the leading digit of a multi-digit number must not be zero.
 
-Write a function to solve alphametics puzzles.
-
 [alphametics]: https://en.wikipedia.org/wiki/Alphametics

exercises/practice/alphametics/.meta/config.json

@@ -27,5 +27,5 @@
     ]
   },
   "test_runner": false,
-  "blurb": "Write a function to solve alphametics puzzles."
+  "blurb": "Given an alphametics puzzle, find the correct solution."
 }