Theorem 8p4e12

Description: 8 + 4 = 12. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	8p4e12	$$⊢8+4=12$$

Proof

Step	Hyp	Ref	Expression
1		8nn0	$$⊢8\in {\mathbb{N}}_0$$
2		3nn0	$$⊢3\in {\mathbb{N}}_0$$
3		1nn0	$$⊢1\in {\mathbb{N}}_0$$
4		df-4	$$⊢4=3+1$$
5		df-2	$$⊢2=1+1$$
6		8p3e11	$$⊢8+3=11$$
7	1 2 3 4 5 6	6p5lem	$$⊢8+4=12$$