reserve k for Nat;

theorem Th8:
  for x be Integer holds SD_Add_Data(x,k) + SD_Add_Carry(x)*Radix(k ) = x
proof
  let x be Integer;
  SD_Add_Data(x,k) + SD_Add_Carry(x)*Radix(k) = x - SD_Add_Carry(x)*Radix(
  k) + SD_Add_Carry(x)*Radix(k) by RADIX_1:def 11;
  hence thesis;
end;
