Metamath Proof Explorer

Theorem 9p2e11

Description: 9 + 2 = 11. (Contributed by Mario Carneiro, 19-Apr-2015) (Revised by AV, 6-Sep-2021)

Ref Expression
Assertion 9p2e11 
|- ( 9 + 2 ) = ; 1 1

Proof

Step Hyp Ref Expression
1 9nn0 
 |-  9 e. NN0
2 1nn0 
 |-  1 e. NN0
3 0nn0 
 |-  0 e. NN0
4 df-2 
 |-  2 = ( 1 + 1 )
5 1e0p1 
 |-  1 = ( 0 + 1 )
6 9p1e10 
 |-  ( 9 + 1 ) = ; 1 0
7 1 2 3 4 5 6 6p5lem 
 |-  ( 9 + 2 ) = ; 1 1