5 x 15000 ÷ 100 = 75015000-750=
Rs 14250
Divide the 5% discount by 100 and multiply it by the amount 15000 and the answer you get 750 is the discount
So subtract 750 from 15000 to get the exact amount he paid 14250
If that is the total after the discount.. gross amouny should be 15789.5 on which discount is calculated.. other just subtract 5% and the net payable is 14250