Metamath Proof Explorer

Theorem 9p8e17

Description: 9 + 8 = 17. (Contributed by Mario Carneiro, 19-Apr-2015)

Ref Expression
Assertion 9p8e17 
|- ( 9 + 8 ) = ; 1 7

Proof

Step Hyp Ref Expression
1 9nn0 
 |-  9 e. NN0
2 7nn0 
 |-  7 e. NN0
3 6nn0 
 |-  6 e. NN0
4 df-8 
 |-  8 = ( 7 + 1 )
5 df-7 
 |-  7 = ( 6 + 1 )
6 9p7e16 
 |-  ( 9 + 7 ) = ; 1 6
7 1 2 3 4 5 6 6p5lem 
 |-  ( 9 + 8 ) = ; 1 7