Question 481419
57 were Zoo members 
but 21 were also Aquarium members
So Only Zoo members = 57-21=36

similarly 32-12 = 11 were members of Aquarium only

11+36+21 =  68 belonged to either one of them or both.

21 belonged to both

Total surveyed = 220 -(11+21+36)
=152 belonged to neither

Circle Z = set of Zoo members
Circle A = set of all aquarium members
Rectangle U = Universal set

<pre><font size = 4 color = "indigo"><b>
{{{drawing(300,300,-4,4,-5,4,
rectangle(-4,-3.5,4,4),
locate(-2,2,11),
locate(-3.5,-2,152)
locate(3,-2.7,U),
circle(sqrt(2),sqrt(2),2), 
locate(-3.5,2.5,A),
circle(-sqrt(2),sqrt(2),2),
locate(3.5,2.5,Z),

locate(0,2.5,21),
locate(2,2,36) )}}}
 
m.ananth@hotmail.ca