Metamath Proof Explorer

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 e. NN0
2 6nn0 
 |-  6 e. NN0
3 4nn0 
 |-  4 e. NN0
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