After 10 years A will be twice the age of B before 10 years.and now if the difference is 9 years between them then what is the age of B after 10 years

Answer: 49a

let present age of a & b is 'A','B' respectively.after 10 yrs age of 'a' is A+10;before 10 yrs age of b is B-10.

given that A+10=2*(B-10)

and A-B=9

by solving above two we get B=39;

so after 10 yrs the age of b is 49