Description: A decimal number is a set. (Contributed by Mario Carneiro, 17-Apr-2015) (Revised by AV, 6-Sep-2021)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | decex | |- ; A B e. _V | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | df-dec | |- ; A B = ( ( ( 9 + 1 ) x. A ) + B ) | |
| 2 | 1 | ovexi | |- ; A B e. _V |