Theorem 8p7e15

Description: 8 + 7 = 15. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	8p7e15	⊢ ( 8 + 7 ) = ; 1 5

Proof

Step	Hyp	Ref	Expression
1		8nn0	⊢ 8 ∈ ℕ0
2		6nn0	⊢ 6 ∈ ℕ0
3		4nn0	⊢ 4 ∈ ℕ0
4		df-7	⊢ 7 = ( 6 + 1 )
5		df-5	⊢ 5 = ( 4 + 1 )
6		8p6e14	⊢ ( 8 + 6 ) = ; 1 4
7	1 2 3 4 5 6	6p5lem	⊢ ( 8 + 7 ) = ; 1 5