Growing up in the United States, I've taken for granted that people communicate sale prices by noting that a product is
X% off. In other words, if a product is typically sold for $100, but is
20% off, the customer pays $80. But, that's not the only way to communicate that concept.
In Denmark, some stores note a sale of
-20%. And in China, sale prices are communicated as a percentage of the original price. So in the example above, someone would say that there is an
80% sale, making the mental math for figuring out how much cash to get out simpler for consumers.
It's interesting what cultures choose to emphasize when communicating the value of a discount. While I'm used to the additional step of subtracting my savings from the original price, there's nothing inherently better about that.