a dishonest dealer professes to sell goods at the cost price but uses a weight of 840 grams per kg , what is his percent ?
"840 - - - 160 100 - - - ? = > 19 % answer : a"
subtract(multiply(divide(const_100, 840), multiply(const_100, multiply(add(const_3, const_2), const_2))), const_100)