Using the formula (b) and replacing the given values:
Sale Price = Original Price - Amount Saved. So,
Sale Price = 1/2 - 0.1
Sale Price = €0.4 (answer).
This means the cost of the item to you is €0.4.
You will pay €0.4 for an item with an original price of €1/2 when discounted 20%.
In this example, if you buy an item at €1/2 with 20% discount, you will pay 0.5 - 0 = 0.4 euros.