Sir these are the question from previous years paper of quantitative aptitude section, pls help

A businessman charges 20% over cost price. He allows his customers 10% off on their bills for cash payment. His net gain percent is??

                           Suppose cost price is =  Rs.  100

                           Marked price                 =   Rs. 120

                           discounted Price          =   Rs. 108

                            Gain                               = Rs. 8    on    Rs. 100  = 8%