sandy is younger than molly by 18 years . if the ratio of their ages is 7 : 9 , how old is sandy ?
"let sandy ' s age be 7 x and let molly ' s age be 9 x . 9 x - 7 x = 18 x = 9 sandy is 63 years old . the answer is d ."
multiply(divide(7, subtract(9, 7)), 18)