Question 529831
We know that P(A,B,AandB,not(A or B)) = 1. In other words, the probability of atleast one of all possible events happening is 1.

So the probability of three of those events is  0.3 + 0.4 + 0.25 as given.

So we have 0.95. Then  1 - 0.95 is the probability of neither happening. 

So it is 0.05.