Problem: a number is doubled and 9 is added . if the resultant is trebled , it becomes 81 . what is that number ?
Rationale: "let the number be x . then , 3 ( 2 x + 9 ) = 81 2 x = 18 = > x = 9 answer : e"
annotated_formula: divide(subtract(81, multiply(const_3, 9)), multiply(const_3, const_2))