Addition of Natural Numbers
a + b = c
The terms of the addition, a and b, are called addends and the result, c is the sum.
Properties of the Addition of Natural Numbers
1. Closure:
The sum of two natural numbers is also a natural number.
a + b 
2. Associative:
The way in which the addends are grouped does not change the result.
(a + b) + c = a + (b + c)
(2+3) + 5 = 2 + (3+5)
5 + 5 = 2 + 8
10 = 10
3. Commutative:
The order of the addends does not change the addition.
a + b = b + a
2 + 5 = 5 + 2
7 = 7
4. Additive identity:
The 0 is the identity element of the addition because every number added with it gives the same number.
a + 0 = a
3 + 0 = 3
