a shop keeper marked 20 % above the cost price and offered 15 % discount then find it ' s net profit ?
net profit = 20 - 15 + ( 20 * ( - 15 ) / 100 ) = 2 % answer is a
subtract(subtract(add(const_100, 20), divide(multiply(add(const_100, 20), 15), const_100)), const_100)