reserve x for set,
  p,q,r,s,t,u for ExtReal,
  g for Real,
  a for Element of ExtREAL;

theorem Th327:
  p <= q implies [.-infty,q.[ \ [.p,s.[ = [.-infty,p.[ \/ [.s,q.[
proof
  -infty <= s by XXREAL_0:5;
  hence thesis by Th302;
end;
