Theorem 9p7e16

Description: 9 + 7 = 16. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	9p7e16	$$⊢9+7=16$$

Proof

Step	Hyp	Ref	Expression
1		9nn0	$$⊢9\in {\mathbb{N}}_0$$
2		6nn0	$$⊢6\in {\mathbb{N}}_0$$
3		5nn0	$$⊢5\in {\mathbb{N}}_0$$
4		df-7	$$⊢7=6+1$$
5		df-6	$$⊢6=5+1$$
6		9p6e15	$$⊢9+6=15$$
7	1 2 3 4 5 6	6p5lem	$$⊢9+7=16$$