Of the 50 entries in a costume contest, 31 entrants were dressed as heroes and 20 entrants were wearing a mask. if 9 entrants were dressed as heroes wearing a mask, how many entrants were neither dressed as heroes nor wearing a mask

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) =

Persons who were neither dressed as heroes nor wearing a mask

area of part 1:

a1=base*height/2=(8+2)*(8-2-2-1)/2=10*3/2=15 ft^2

area of part 2:

a2=length*width=(8+2)*1=10 ft2

area of part 3:

a3=length*width=8*2=16 ft2

total shaded area : a1+a2+a3=41 ft2

total area of the reactangle : a=16*8=128 ft2

total area of the nonshaded region : 128-41=87 ft2

29 mil

step-by-step explanation: