The probability that a leap year will have 53 Fridays or 53 Saturdays is

Leap year has 52 weeks and 2 more days. For 53 Fridays those two should be Thursday, Friday or Friday, Saturday. Hence probability of 53 Fridays

Similarly probability of 53 Saturdays

Let these two events be A and B respectively.

Now A and B can't occur simultaneously as there can't be any pair consisting of Friday and Saturday.

So P(A or B) = P(A)+P(B)-P(AB) =