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Three iPhones are selected at random.

A is the event of selecting at least one defective iPhone.

A and $\stackrel{炉}{A}$are said to be complementary when the former denotes the occurrence of the event and the latter denotes the non-occurrence of the event or vice-versa.

Thus, the outcomes of event A are opposite (all elements of sample space except those supportive of A) to $\stackrel{炉}{A}$.

The following property holds true for the probability of complementary events:

$P\left(A\right)+P\left(\stackrel{炉}{A}\right)=1$

A is the event of selecting at least one defective iPhone. Therefore,the number of defective iPhones selected is 1, 2, or 3 in the three randomly selected iPhones.

Thus, is the event of 鈥渘ot鈥� selecting at least one defective iPhone. In other words, it is an event of not selecting any (0) defective iPhone.