Problem: in what ratio must rice of rs . 25 per kg be mixed with rice of rs . 12 per kg so that cost of mixture is rs . 20 per kg ?
Rationale: "( 20 - 12 ) / ( 25 - 20 = 8 / 5 = 8 : 5 answer : a"
annotated_formula: divide(divide(subtract(20, 12), subtract(25, 12)), subtract(const_1, divide(subtract(20, 12), subtract(25, 12))))