WHAT IS 15.7188888888 X 18 TO THE POWER OF SIX DIVIDED BY 7 Plus 3

Aparallel system functions whenever at least one of its components works. consider a parallel system of n components, and suppose each component works independently with probability 0.5. find the conditional probability that component n works given that the system is working

In a column proof the right column states your reasons

The anwser cause i do not understand just plez