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  Pick one:
A) 37 B) 38 C) 39 D) 40 E) 41

Rationale: "let present age of a be a and b be b a + 10 = 2 * ( b - 10 ) = > 2 b - a = 30 . . . . . . ( i ) a = b + 9 = > 2 b - b - 9 = 30 b = 39 so the present age of b is 39 years answer : c"
Answer: C