In a survey of 300 individual investors regarding subscription to the NYT, WSJ, and UST....:

Question

122 sub to NYT
150 sub to WSJ
62 sub to UST
38 sub to NYT and WSJ
20 sub to NYT and UST
28 sub to WSJ and UST

b) How many individual investors surveys subscribe to only one of the investors?
I just added the outermost parts of my venn diagrams (68+84+14) for 162.

c) How many investors subscribe to only one newspaper?
I am confused. Is this the same as part b???

Answer 1

You are not accounting for people subscribing to all 3
which would be included in the double intersection values of 38, 20, and 28

n(N or W or U) = n(W) + n(N) + n(U) - n(W and N) - n(W and U) - n(N and U) + n(W and N and U)
300 = 150+122+62 - 38 - 28 - 20 + n(W and N and U)
52 = n(W and N and U)

So 52 take all 3 papers
but n(W and N and U) ≤ 20 , or else the intersection of two at a time are negative.

so I think your data is inconsistent