A bicycle costs 72 dollars after a 20% discount. Which calculation does NOT recover the original price by the reverse-percentage method?

توضیح

The original price satisfies 0.80 times the original equals 72, so dividing 72 by 0.80 gives 90. The calculation 72 + 0.20 × 72 = 86.40 wrongly takes the discount from the final sale price.