First of all, I am sorry for my bad english, I am from Brazil :-) I have problem with proof for some set theory task.
Here it is:
$A,B,C$ are three sets. Show that:
$$(A\setminus B) \subset (A\setminus C) \cup (C\setminus B)$$
It is clear by looking at diagrams but I do not know how I show! It is not too hard I think...
Thank you for the help,