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

theorem Th336:
  for s being Real holds p <= q
  implies ].-infty,q.] \ [.p,s.[ = ].-infty,p.[ \/ [.s,q.]
proof
  let s be Real;
  s in REAL by XREAL_0:def 1;
  hence thesis by Th303,XXREAL_0:12;
end;
