a watch was sold at a loss of 20 % . if it was sold for rs . 520 more , there would have been a gain of 6 % . what is the cost price ?
"80 % 106 % - - - - - - - - 26 % - - - - 520 100 % - - - - ? = > rs . 2000 answer : b"
divide(multiply(520, const_100), subtract(add(const_100, 6), subtract(const_100, 20)))