Theorem 9p3e12

Description: 9 + 3 = 12. (Contributed by Mario Carneiro, 19-Apr-2015)

	Ref	Expression
Assertion	9p3e12	|- ( 9 + 3 ) = ; 1 2

Proof

Step	Hyp	Ref	Expression
1		9nn0	|- 9 e. NN0
2		2nn0	|- 2 e. NN0
3		1nn0	|- 1 e. NN0
4		df-3	|- 3 = ( 2 + 1 )
5		df-2	|- 2 = ( 1 + 1 )
6		9p2e11	|- ( 9 + 2 ) = ; 1 1
7	1 2 3 4 5 6	6p5lem	|- ( 9 + 3 ) = ; 1 2