Theorem 8p4e12

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

	Ref	Expression
Assertion	8p4e12	⊢ ( 8 + 4 ) = ; 1 2

Proof

Step	Hyp	Ref	Expression
1		8nn0	⊢ 8 ∈ ℕ0
2		3nn0	⊢ 3 ∈ ℕ0
3		1nn0	⊢ 1 ∈ ℕ0
4		df-4	⊢ 4 = ( 3 + 1 )
5		df-2	⊢ 2 = ( 1 + 1 )
6		8p3e11	⊢ ( 8 + 3 ) = ; 1 1
7	1 2 3 4 5 6	6p5lem	⊢ ( 8 + 4 ) = ; 1 2