in what ratio must rice at $ 9.30 / kg be mixed with rice at $ 10.80 / kg so that the mixture is worth $ 10 / kg ?
9.30 x + 10.80 y = 10 ( x + y ) . 80 y = . 70 x x / y = 8 / 7 c is the answer
divide(subtract(10.8, 10), subtract(10, 9.3))