Problem: two numbers are respectively 50 % and 20 % more than a third number . the percentage that is first of the second is ?
Rationale: "i ii iii 150 120 100 120 - - - - - - - - - - 150 100 - - - - - - - - - - - ? = > 125 % answer : a"
annotated_formula: subtract(const_100, multiply(divide(add(50, const_100), add(20, const_100)), const_100))