Sandy is younger than Molly by 18 years. If the ratio of their ages is 7:9, how old is Sandy?  Choose one.
A) 42
B) 49
C) 56
D) 63
E) 70
Let Sandy's age be 7x and let Molly's age be 9x.   9x - 7x = 18   x = 9   Sandy is 63 years old.   The answer is 63.
<result>D</result>
Sandy is younger than Molly by 18 years. If the ratio of their ages is 7:9, how old is Sandy?