The explanation for the 1st one , the official answer 20 is correct : n(1) = 50 n(2) = 30 n(3) = 20 What is asked is the % of consumers who liked more than one product, which means : n(A int B) + n(B int C) + n(A int C) n(A) + n(B) + n(C) - n(AUBUC) + n(A int B int C) (derived from the formula of AU...