Use a Venn Diagram or Some Other Method to Obtain $n ( L \cup M \cup N )$

Essay

Use a Venn diagram or some other method to obtain a formula for
$n ( L \cup M \cup N )$
in terms of
$n ( L )$
n $( M )$
$n ( N )$
$n ( L \cap M )$
$n ( L \cap N )$
$n ( M \cap N )$
, and
$n ( L \cap M \cap N )$