Theorem 9p2e11

Description: 9 + 2 = 11. (Contributed by Mario Carneiro, 19-Apr-2015) (Revised by AV, 6-Sep-2021)

	Ref	Expression
Assertion	9p2e11	$$⊢9+2=11$$

Proof

Step	Hyp	Ref	Expression
1		9nn0	$$⊢9\in {\mathbb{N}}_0$$
2		1nn0	$$⊢1\in {\mathbb{N}}_0$$
3		0nn0	$$⊢0\in {\mathbb{N}}_0$$
4		df-2	$$⊢2=1+1$$
5		1e0p1	$$⊢1=0+1$$
6		9p1e10	$$⊢9+1=10$$
7	1 2 3 4 5 6	6p5lem	$$⊢9+2=11$$