
theorem
  for L being non empty doubleLoopStr, A, B being non empty Subset of L
  st A c= B holds A-RightIdeal c= B-RightIdeal
proof
  let L be non empty doubleLoopStr, A,B be non empty Subset of L;
  assume
A1: A c= B;
  B c= B-RightIdeal by Def16;
  then A c= B-RightIdeal by A1;
  hence thesis by Def16;
end;
