A system is composed by three components A, B, C working in parallel and failure in one component is independent of any other failure in another component. The realiability (probability of a component working well) of each of the three components is equal to p. Failure of the system occurs when all three components fail. The Reliability of the system is 

If A, B and C are three mutually exclusive events, where A and B are exhaustive and C independent from A and B, so for every event D we can write

A, B and C are three events such that A and B are indepedent; then

If two events A and B are independent then

If two events, noted A and B , are mutually exclusive and exhaustive we have: