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?  Select the correct option:
A) 39 yr B) 42 yr C) 45 yr D) 32 yr E) 50 yr

Rationale: "let b ' s present age = x years then a ' s present age = x + 9 years x + 9 + 10 = 2 ( x - 10 ) x + 19 = 2 x - 20 x = 39 years answer is a"
Answer: A