 reserve x for Real,
    p,k,l,m,n,s,h,i,j,k1,t,t1 for Nat,
    X for Subset of REAL;
reserve x for object, X,Y,Z for set;
 reserve M,N for Cardinal;

theorem
  for X,Y being finite set st X c= Y holds card X <= card Y
 proof let X,Y be finite set;
  assume X c= Y;
   then Segm card X c= Segm card Y by CARD_1:11;
  hence card X <= card Y by Th27;
 end;
