Theorem 6p6e12

Description: 6 + 6 = 12. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	6p6e12	$$⊢6+6=12$$

Proof

Step	Hyp	Ref	Expression
1		6nn0	$$⊢6\in {\mathbb{N}}_0$$
2		5nn0	$$⊢5\in {\mathbb{N}}_0$$
3		1nn0	$$⊢1\in {\mathbb{N}}_0$$
4		df-6	$$⊢6=5+1$$
5		df-2	$$⊢2=1+1$$
6		6p5e11	$$⊢6+5=11$$
7	1 2 3 4 5 6	6p5lem	$$⊢6+6=12$$