Theorem 7p7e14

Description: 7 + 7 = 14. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	7p7e14	$$⊢7+7=14$$

Proof

Step	Hyp	Ref	Expression
1		7nn0	$$⊢7\in {\mathbb{N}}_0$$
2		6nn0	$$⊢6\in {\mathbb{N}}_0$$
3		3nn0	$$⊢3\in {\mathbb{N}}_0$$
4		df-7	$$⊢7=6+1$$
5		df-4	$$⊢4=3+1$$
6		7p6e13	$$⊢7+6=13$$
7	1 2 3 4 5 6	6p5lem	$$⊢7+7=14$$