some of 10 % - intensity red paint is replaced with 20 % solution of red paint such that the new paint intensity is 15 % . what fraction of the original paint was replaced ?
"let total paint = 1 let amount replaced = x 10 ( 1 - x ) + 20 x = 15 x = 1 / 2 answer : c"
divide(subtract(divide(15, const_100), divide(10, const_100)), subtract(divide(20, const_100), divide(10, const_100)))