 reserve x,y,X,Y for set;
reserve G for non empty multMagma,
  D for set,
  a,b,c,r,l for Element of G;
reserve M for non empty multLoopStr;

theorem Th21:
  for G being multMagma, M being MonoidalSubStr of G holds M is SubStr of G
proof
  let G be multMagma, M be MonoidalSubStr of G;
  thus op(M) c= op(G) by Def24;
end;
