
theorem Th7:
  for L being meet-absorbing join-absorbing meet-associative non
empty LattStr, a, b, c being Element of L holds a [= b implies a"/\"c [= b"/\"
  c
proof
  let L be meet-absorbing join-absorbing meet-associative non empty LattStr,
  a, b, c be Element of L;
  assume a [= b;
  hence (a"/\"c)"\/"(b"/\"c) = ((a"/\"b)"/\"c)"\/"(b"/\"c) by Th2
    .= (a"/\"(b"/\"c))"\/"(b"/\"c) by Def7
    .= b"/\"c by Def8;
end;
