The discount amount for the baby formula is $20.00 - $12.00 = $8.00.
To find the percentage discount:
Discount percentage = (Discount amount ÷ Regular price) x 100%
Discount percentage = ($8.00 ÷ $20.00) x 100%
Discount percentage = 0.4 x 100%
Discount percentage = 40%
Therefore, the percentage discount for the baby formula sale is 40%.