1. The problem statement, all variables and given/known data Three people work independently at deciphering a message sent in code. the respective probabilities are persion a: 1/6 person b: 1/8 person c: 2/7 what is the probability that the message will be decoded 2. Relevant equations (A or B ) = Pr(A) + Pr(b) - Pr(A and B) A' = 1 - A 3. The attempt at a solution My first solution was: decoded message = Pr(A) + Pr(b) + Pr(C) - ( Pr(A)Pr(b)Pr(c) + Pr(A)Pr(B) + Pr(A)Pr(c) + Pr(B)Pr(c)) and I thought it made sense, apparently the answer is not the same. The actual answer is taking the inverse decoded = ( 1 - Pr(A) ) + ( 1 - Pr(B) ) + ( 1 - Pr(C) ) I understand this method, But I was curious why doesnt my method work?