a watch was sold at a loss of 10 % . if it was sold for rs . 280 more , there would have been a gain of 4 % . what is the cost price ?
"90 % 104 % - - - - - - - - 14 % - - - - 280 100 % - - - - ? = > rs : 2000 answer : a"
divide(multiply(280, const_100), subtract(add(const_100, 4), subtract(const_100, 10)))