Correct indent

Otherwise the content won't be shown under the item number 2.

ch02/2.2/2.2.md

@@ -118,23 +118,23 @@ the following languages. In each case show that your grammar is correct.
 2. No. Consider the string "10101", which is divisible by 3, but cannot be
    derived from the grammar.
 
-   Readers seeking a more formal proof can read about it below:
+    Readers seeking a more formal proof can read about it below:
 
-   **Proof**:
+    **Proof**:
 
-   Every number divisible by 3 can be written in the form `3k`. We will consider `k > 0` (though it would be valid to consider `k` to be an arbitrary integer).
+    Every number divisible by 3 can be written in the form `3k`. We will consider `k > 0` (though it would be valid to consider `k` to be an arbitrary integer).
 
-   Note that every part of num(11, 1001 and 0) is divisible by 3, if the grammar could generate all the numbers divisible by 3, we can get a production for binary k from num's production:
+    Note that every part of num(11, 1001 and 0) is divisible by 3, if the grammar could generate all the numbers divisible by 3, we can get a production for binary k from num's production:
 
-   ```
-   3k = num   -> 11 | 1001 | num 0 | num num
-    k = num/3 -> 01 | 0011 | k 0 | k k
-    k         -> 01 | 0011 | k 0 | k k
-   ```
+    ```
+    3k = num   -> 11 | 1001 | num 0 | num num
+     k = num/3 -> 01 | 0011 | k 0   | k k
+     k         -> 01 | 0011 | k 0   | k k
+    ```
 
-   It is obvious that any value of `k` that has more than 2 consecutive bits set to 1 can never be produced. This can be confirmed by the example given in the beginning:
+    It is obvious that any value of `k` that has more than 2 consecutive bits set to 1 can never be produced. This can be confirmed by the example given in the beginning:
 
-   10101 is 3*7, hence, k = 7 = 111 in binary. Because 111 has more than 2 consecutive 1's in binary, the grammar will never produce 21
+    10101 is 3*7, hence, k = 7 = 111 in binary. Because 111 has more than 2 consecutive 1's in binary, the grammar will never produce 21
 
 
 ### 2.2.6