In 10 years, A will be twice as old5as B was 10 years ago. If A is now 9 years older than B, the present age of B is Choose the correct choice from the following answers:
A) 16 years  B) 88 years  C) 39 years  D) 66 years  E) 77 years

Rationale: "let b ' s age = x years . then , as age = ( x + 9 ) years . ( x + 9 + 10 ) = 2 ( x — 10 ) hence x = 39 . present age of b = 39 years answer : c"
Answer: C