Answer : We know that,

If odds in favor of the occurrence an event are a:b, then the probability of an event to occur is    , which indirectly came from

Probability of the occurrence of an event

Where, Total no.of desired outcomes = a, and total no.of outcomes = a+b Given a = 8, b= 13

The probability that the event occurs a/a+b

8/8+13

8/21

Conclusion: Probability that the event occurs is 8/21