Here is a good Venn diagram site
with the basics for review:
Basics about Venn diagrams
Rules for set manipulation:
(a) Distributive Rule:
.
(b) De Morgan's Laws:
.
More generally
.
and for a definitely more colorful set of web pages about Venn diagrams please click Here is a sophisticated Venn site
Events are said to be mutually
exclusive if
Note that this is a property of the sets, not of the probability.