reserve T for non empty Abelian
  add-associative right_zeroed right_complementable RLSStruct,
  X,Y,Z,B,C,B1,B2 for Subset of T,
  x,y,p for Point of T;

theorem
  B (+) (X/\Y) c= (B (+) X)/\(B (+) Y)
proof
  B (+) (X/\Y) = (X/\Y) (+) B by Th12;
  then B (+) (X/\Y) c= (X (+) B)/\(Y (+) B) by Th34;
  then B (+) (X/\Y) c= (B (+) X)/\(Y (+) B) by Th12;
  hence thesis by Th12;
end;
