Answer:
8
Step-by-step explanation:
Given that Of the 50 entries in a costume contest, 31 entrants were dressed as heroes and 20 entrants were wearing a mask. 9 entrants were dressed as heroes wearing a mask.
Let A = heroes and B = wearing mask
n(U) = 50
n(A)=31 and n(B) = 20 and n(AB) =9
Hence n(AUB) = [tex]31+20-9 = 42[/tex]
Persons who were neither dressed as heroes nor wearing a mask
[tex]= n(U)-n(AUB)\\= 50-42=8[/tex]
