reserve x for set;

theorem Th7:
  for L being LATTICE for a,b,c being Element of L holds
  a"\/"(b"/\"c) <= (a"\/"b)"/\"(a"\/"c)
proof
  let L be LATTICE;
  let a,b,c be Element of L;
A1: a <= a;
  b"/\"c <= c by YELLOW_0:23;
  then
A2: a"\/"(b"/\"c) <= a"\/"c by A1,YELLOW_3:3;
  b"/\"c <= b by YELLOW_0:23;
  then a"\/"(b"/\"c) <= a"\/"b by A1,YELLOW_3:3;
  hence thesis by A2,YELLOW_0:23;
end;
