Theorem 7p6e13

Description: 7 + 6 = 13. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	7p6e13	$$⊢7+6=13$$

Proof

Step	Hyp	Ref	Expression
1		7nn0	$$⊢7\in {\mathbb{N}}_0$$
2		5nn0	$$⊢5\in {\mathbb{N}}_0$$
3		2nn0	$$⊢2\in {\mathbb{N}}_0$$
4		df-6	$$⊢6=5+1$$
5		df-3	$$⊢3=2+1$$
6		7p5e12	$$⊢7+5=12$$
7	1 2 3 4 5 6	6p5lem	$$⊢7+6=13$$