In 10 years, A will be twice as old as B was 10 years ago. If A is now 9 years older than B, the present age of B is Choose the most appropriate option.
A) 9 years  B) 19 years  C) 29 years  D) 39 years  E) None
Solution   Let B's present age	= x years.   Then, A's present age	‹=› (x + 9) years.   ∴(x + 9) + 10 = 2 (x - 10)   ‹=› x + 19 = 2x - 20   ‹=› x = 39.   Answer 39 years
<result>D</result>
In 10 years, A will be twice as old as B was 10 years ago. If A is now 9 years older than B, the present age of B is