Answer:
We would need to know the percentage of discount offered during the sale to determine the sale price of the polo shirt. Here's an example calculation for a 25% discount:
If the discount offered is 25%, Bert will only need to pay 75% of the original price. We can calculate this as:
Sale price = (100% - 25%) x $20
Sale price = 75% x $20
Sale price = 0.75 x $20
Sale price = $15
Therefore, if the discount offered during the sale is 25%, Bert will pay $15 for the polo shirt. However, if the discount is different, the sale price will be different.