For a parallel structure of identical components, the system can succeed if at least one of the components succeeds. assume that components fail independently of each other and that each component has a 0.11
(a) would it be unusual to observe one component fail?
would it be unusual to observe two components fail?
(b) what is the probability that a parallel structure with 2 identical components will succeed?
the probability that a parallel structure with 2 identical components will succeed is
(type an integer or a decimal. do not round.)
(c) how many components would be needed in the structure so that the probability the system will succeed is greater than 0.?
(round up to the nearest whole number.)

1) If you ever come across a situation where components fail independently of each other and that each component has a 0.11 it won'be unsusual because such percent as 11% is quite frequent and common.

2) If two components fail, that will definitely be unusual as the percent greatly increases : 11%*11%=1,21% - it is not as common as in previous situation.

3) Here is the way how you can get the probability that a parallel structure with 2 identical components will succeed :
you have to take the obtained percent away from 100% 
100-1,21=98,79 

4) The number of components that  will be needed in the structure so that the probability the system will succeed is greater than .9999 is being shown below: 

then just round it up.
Do hope that will help you!

555%=6786666vgggcccf