Maths - Algebraic proof

Proof - What is N?

Proof - What do 2 consecutive numbers equal?

Proof - What do 3 consecutive numbers equal?

Proof - What does an even number equal?

Proof - What do 2 consecutive even numbers equal?

Proof - What do 3 consecutive even numbers equal?

Proof - What does an odd number equal?

Proof - What do 2 consecutive odd numbers equal?

Proof - What do 3 consecutive odd numbers equal?

Proof - What do 2 even numbers equal?

Proof - What do 2 odd numbers equal?