Question

What is the probability that a client chooses Greece, or Italy, or both countries, on a tour?

Answer 1

The probability a client will choose Greece is shown by  notation
P (G)
The probability a client will choose Italy is shown by
P (I)
The probability a client will choose both is shown by
P (G and I) = P (G ∩ I) = P (G) × P(I)

Answer 2

1/3 is the probability. There are 3 options, and they may only choose one - Greece, Italy, or both.