Answer:
To calculate the cost of the watch after a 20% discount, you need to subtract the discount amount from the original price.
The discount percentage is 20%, which can be converted to a decimal by dividing 20 by 100: 20 / 100 = 0.2.
Now, let's calculate the discount amount:
Discount amount = 0.2 * $280 = $56.
To find the final cost after the discount, subtract the discount amount from the original price:
Final cost = $280 - $56 = $224.
Therefore, the watch costs $224 after a 20% discount.