Section 5.3 Exercise 18

A group of 100 workers were asked if they were college graduates 
and if they belonged to a union. Sixty were not college graduates, 20
were nonunion college graduates, and 30 were union members. 

How many were neither college graduates nor union members?

U = the workers surveyed. n(U) = 100
G = college graduates
M = union members

We have n(M' intersect G) = 20, n(G') = 60, and n(M) = 30.