Problem: the difference between a number and its two - fifth is 510 . what is 20 % of that number ?
Rationale: "let the number be x . then , x - 2 / 5 x = 510 x = ( 510 * 5 ) / 3 = 850 20 % of 850 = 170 . answer : b"
annotated_formula: divide(multiply(510, add(const_4, const_1)), add(const_1, const_2))