A shopkeeper marks his goods 15% above the cost price, but allows 20% discount for cash. His net loss is = ?

Let the cost price be Rs. 100
then the mark up price which is 15% above the cost price,
Mark price = (100 + 15% of 100) = Rs. 115
Shopkeeper gives a discount of 20% on mark up price, then the
Selling Price = (115 - 20% of 115) = Rs. 92
loss = 92 - 100 = Rs. -8
$$\eqalign{ & \% {\text{loss}} = \frac{{ - 8 \times 100}}{{100}} = - 8\% \cr & \therefore {\text{loss}} = 8\% \cr} $$