probability

There are 52 sundays in a non leap year.

so in a leap year the two extra days(366=364+2)

there are seven  possibilities for the extra day

i.e. the sample space isS={ mon,-tue, tue-wed...sat- sun,sun-mon} (7 possibilities)..n(S)=7

out of which two cases are fav for  the event of having a sunday..n(E)=2

so the prob of there being 53 sundays is

n(E)/n(s)=2/7.