How to Disprove $A-(B-C)=A-(B\cup C)$? For $A,B,C$ sets. I know I want to show that it is not the case that $A-(B-C)$ is not equal to $A-(B\cup C)$, I also know that the definition of set deference is x is an element in A but not in B if I have set A-B, but to disprove this is getting a bit difficult. 

Suppose $B$ is a non-empty subset of $A$ and $B=C.$ Then the LHS is $A$ and the RHS is $A$ \ $B$ which is not equal to $A.$ So the equation cannot be true for all $A,B,C.$ 
