Mathematics, statistic 150 EqualProbabilities

Question

Suppose that X  is an event, and that P(X)=0.43 . What is P(X)  (i.e. the probability that  will not occur)?

Answer = 

Answer 1

An event will either occur or not occur.

Therefore, the probability an event will occur + The probability an event will NOT occur = 1.

so that the probability an event will NOT occur = 1 - The probability an event will occur

Thus if P(X) = 0.43, then P(not X) = 1 - 0.43 = 0.57.