⟩ 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?
A+10=2(B-10)
&
A-B=9 i.e. A=B+9,
now,
putting it in earlier eqn.
B+19=2B-20
so B=39,
after 10 years B will be 39+10=49.
Ans =49