IMO C
wats OA?

from the question we need to know how many years have passed by.
let no. of yrs. passed b/w their marr. and div. be x.A is ann's age and M is man's age.
So the equation thus formed is A+x = 2/3(M+x).
statement 1) M+x=2S;S is mistress's age.insuff
statement 2) S=(A=x)-10; insuff
taking both equations and substiuting last equation in above equations
we get A+x = 40 and M+x = 60;
so when they got married they were 20,40
hence they divorced in 2000.

hence C