Fixed block code and syntax highlighting (#29977)

This commit fixes the example code to demonstrate the working of arithmetic operators so that the entire code, from initial comment to ending curly brace for main(), is in a Markdown code block and is syntax highlighted.  Spacing around the include and int initialization was improved as well.

guide/english/c/operators/index.md

@@ -50,12 +50,13 @@ Operators in C specifies the Mathematical, Conditional and Logical Operations to
      int c = --a; // prefix operator; a = 5, c = 5
      ```
 
- C Program to demonstrate the working of arithmetic operators
+ - C Program to demonstrate the working of arithmetic operators
 ```C
 #include <stdio.h>
+
 int main()
 {
-    int a = 9,b = 4, c;
+    int a = 9, b = 4, c;
     
     c = a+b;
     printf("a+b = %d \n",c);