Theorem 9p4e13

Description: 9 + 4 = 13. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	9p4e13	⊢ ( 9 + 4 ) = ; 1 3

Proof

Step	Hyp	Ref	Expression
1		9nn0	⊢ 9 ∈ ℕ0
2		3nn0	⊢ 3 ∈ ℕ0
3		2nn0	⊢ 2 ∈ ℕ0
4		df-4	⊢ 4 = ( 3 + 1 )
5		df-3	⊢ 3 = ( 2 + 1 )
6		9p3e12	⊢ ( 9 + 3 ) = ; 1 2
7	1 2 3 4 5 6	6p5lem	⊢ ( 9 + 4 ) = ; 1 3