 reserve x for Real,
    p,k,l,m,n,s,h,i,j,k1,t,t1 for Nat,
    X for Subset of REAL;

theorem Th16:
  for n,k being natural Number holds k <> 0 implies n < n + k
proof
  let n,k be natural Number;
  assume k <> 0;
  then
A1: n <> n + k;
  n <= n + k by Th12;
  hence thesis by A1,XXREAL_0:1;
end;
