Let A and B are two events.

As, out of 2 events A and B only one can happen at a time which means no event have anything common.

∴ We can say that A and B are mutually exclusive events.

By definition of mutually exclusive events we know that:

P(A ∪ B) = P(A) + P(B)

According to question one event must happen.

This implies A or B is a sure event.

∴ P(A ∪ B) = P(A) + P(B) = 1 …Equation 1

Given, P(A) = (2/3)P(B)

To find: odds in favour of B

∴

⇒

∴ P(B’) = 1 – 3/5 = 2/5

∴ Odd in favour of B =