(a + b) + 1 = (a + b) + 1
a + (b + (c + 1)) = (a + (b + c)) + 1 } (a + b) + c = (a + b) + c
(a + b) + (c + 1) = ((a + b) + c) + 1

      (a + b) + 1 = (a + b) + 1
(a + b) + 1 = (b + a) + 1
(1 + b) + 1 = b + (1 + 1)

a + (b + 1) = (a + b) + 1

(b + 1) + a = (b + a) + 1



a + 1 = a + 1
1 + a = a + 1


      (a + 1) + 1 = (a + 1) + 1       (1 + (a) + 1) = (1 + a) + 1       a + (b + 1) = (a + b) + 1

(a + 1) + 1 = (a + 1) + 1
}a + 1 = 1 + a
1 + (a + 1) = (1 + a) + 1
a + b = b + a

a + (b + 1) = (a + b) + 1
((b + 1) + a) = (b + a) + 1



(b + 1) + a
II
=
(1 + b) + a
I
=
1 + (b + a)
II
=
(b + a) + 1
1 + (b + a) = (1 + b) + a