reserve a,b,p,k,l,m,n,s,h,i,j,t,i1,i2 for natural Number;

theorem Th50:
  i>=i1 implies i>=i1-'i2
proof
  assume
A1: i>=i1;
  i1>=i1-'i2 by Th35;
  hence thesis by A1,XXREAL_0:2;
end;
