sandy is younger than molly by 20 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 = 20 x = 10 sandy is 70 years old . the answer is e ."
multiply(divide(7, subtract(9, 7)), 20)