For two sets A,B with $B\subset A$ let us define:
$$A-B:=A\setminus B $$
as the monotone difference. If $B$ is not a subset of $A$ then $A-B$ is not defined. Now my question. How to portray $A \cup B$ with only $-$ and $\cap$?
Thanks for hints and/or solutions.
My idea: $$A \cup B=(X-A-B)^c$$
But I guess I cannot use complement.
So this would mean: $$A \cup B=X-(X-A-B)$$
Or, if $\cap$ has to be used: $$A \cup B=X-(X-(A-(A \cap B))-(B-(A \cap B))-(A \cap B))$$