Hex addition (#20950)

* Hex addition

I added how to add hexadecimal numbers.

* Apply code formatting

guide/english/mathematics/hexadecimal-number-system/index.md

@@ -5,7 +5,53 @@ title: Hexadecimal Number System
 Hexadecimal number system is a numbering system that uses base 16. Hexa = 6 and decimal = 10, combination of 'hexa' and 'decimal' gives use the base 16 number system. The numbers in hexadecimal are: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 = A, 11 = B, 12 = C, 13 = D, 14 = E and 15 = F.
 The hexadecimal number system is very useful in the field of computing like Cryptography.
 
+## Adding Hexadecimal Numbers:
+
+Adding hex numbers are just like adding decimal with a twist.
+
+Lets look at the example below:
+```
+ 0x14
++0x10
+______
+ 0x24
+ ```
+
+`4 + 0 = 4` and `1 + 1 = 2`. Simple, right? 
+ 
+ How about when there is a carry over?
+ ```
+   0x1A
+ + 0x1B
+ _______
+   0x
+```
+
+`A(10) + B(11) = 21`. `21 % 16 = 5`.
+
+```
+     1
+   0x1A
+ + 0x1B
+ _______
+   0x 5
+```
+Now, `1 + 1 + 1 = 3`. Thus,
+   
+```
+     1
+   0x1A
+ + 0x1B
+ _______
+   0x35
+```
+
+When there is a carry over in hex (meaning two numbers adding together is greater than 15), mod the number by 16 and carry a one over. 
+This is analogous to the decimal system.
+  
 #### More Information:
-<a href='https://en.m.wikipedia.org/wiki/Hexadecimal'>Wikipedia</a>
+- <a href='https://en.m.wikipedia.org/wiki/Hexadecimal'>Wikipedia</a>
+- [Hex Calc](https://www.calculator.net/hex-calculator.html)
+