What is the error in the following code(Below)? | PL SQL

Declare
vx number;
vy number;
1_result number;
2_result number;
Begin
vx :=10;
vy :=20;
1_result :=vx*vy;
2_result :=vx+vy;
End;
   The variable names in PL/SQL cannot begin, with a numeric character. In PL/SQL, identifier should begin with an alphabet.