Sandy is younger than Molly by 16 years. If the ratio of their ages is 7:9, how old is Sandy? Select: A) 42 B) 49 C) 56 D) 63 E) 70

Rationale: "let sandy ' s age be 7 x and let molly ' s age be 9 x . 9 x - 7 x = 16 x = 8 sandy is 56 years old . the answer is c ."
Answer: C