Percentage Discount given an Original Price of $28 and a Sale Price of $20

Discount Rate = 1 –  
Discount Rate = 1 – 0.7143
Discount Rate = 0.2857
0.2857 Converted to a Percent: 0.2857 = 28.57%
Percentage Discount given an Original Price of $28 and a Sale Price of $20 = 28.57%
Note: Reduction in Price = $28 – $20 = $8