If an event has a probability P of happening, then there is a probability of (1-P) of the event not happening.
In this case the probability of the event is p=20/69.
Then, the probability of the event not happening is:
[tex]P(\text{not happening})=1-p=1-\frac{20}{69}=\frac{69-20}{69}=\frac{49}{69}[/tex]Answer: the probability of the event not happening is 49/69.
