The months whose names end in 'y' include Jan, Feb, May, Jul. The probability of randomly selecting a month whose name ends in 'y' is 4/12 (remember that there are 12 months in a year), or 1/3.
Thus, the probability of selecting a month whose name does NOT end in 'y' is 8/12, or 2/3. Note that this event is the 'complement' of the first event:
P(name does not end in 'y') = 1 - P(name does not end in 'y') = 1 - 1/3 = 2/3
