Final answer:
The sale price of the polo shirt cannot be determined without knowing the discount rate or amount. To find the sale price with a known discount, you subtract the discount from the original price.
Step-by-step explanation:
To determine the sale price of the polo shirt, we would need to know the discount amount or percentage off the original price. Since the question does not provide this information, we cannot calculate the exact sale price. However, if the discount rate or amount were provided, you would subtract the discount from the original price of $20 to find the sale price.
For example, if the shirt is on a 20% discount, you would convert the percentage to a decimal (0.2) and multiply it by the original price ($20) to get the discount amount ($4). Then subtract the discount amount from the original price: $20 - $4 = $16, which would be the sale price.