Theorem 9p8e17

Description: 9 + 8 = 17. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	9p8e17	$$⊢9+8=17$$

Proof

Step	Hyp	Ref	Expression
1		9nn0	$$⊢9\in {\mathbb{N}}_0$$
2		7nn0	$$⊢7\in {\mathbb{N}}_0$$
3		6nn0	$$⊢6\in {\mathbb{N}}_0$$
4		df-8	$$⊢8=7+1$$
5		df-7	$$⊢7=6+1$$
6		9p7e16	$$⊢9+7=16$$
7	1 2 3 4 5 6	6p5lem	$$⊢9+8=17$$