Price of the book = Rs 18.90
Price of the pen = Rs 8.50
Price of the paper = Rs 5.05
Total price of the three items = Rs 18.90 + Rs 8.50 + Rs 5.05
= Rs 32.45
Total amount given to the shopkeeper = Rs 50
Therefore, balance received from the shopkeeper
= Total amount given to the shopkeeper - total price of the three items
= Rs 50 - Rs 32.45
= Rs 17.55