Question 174556
what you need to do is draw 3 circles that all intersect
exactly like the olympic circles
The circles represent steak, pasta, and salad
steak = 11
pasta = 16
salad = 16
The 5 who want salad and steak are the intersection
of the steak and salad circles
3 of those are in the pasta circle
The steak circle is made up of 
5 want only steak
5 want steak and salad
{{{11 - (5+5) = 1}}} so,
1 wants steak and pasta
8 want only pasta
3 want pasta,steak and salad
{{{16 - (8 + 1 + 3) = 4}}} so,
4 want salad and pasta
3 want all the items 
2 want steak and salad
{{{16 - (2 + 3 + 4) = 7}}} so,
7 people want salad only
(unless I goofed)