​If the original price of an item is x...

​A markdown or discount will be a part of x. That is, it will be a value less than 100% of x.

​

​Example.

​A store is having a sale and discounting items by 25%. The amount saved, or discounted is 25% of x.

​0.25x

​The new sale price is also a part of x.

​​Example.

​A store is having a sale and discounting items by 25%. The amount saved, or discount is 25% of x.

​0.25x

​

​The sale price will be (100% - 25%) of x, or 75% of x.

​0.75x

​

​The equation for the discount is y=0.25x.

​The equation for the sale price is y=0.75x

​​If the original price of an item is x...

​A markup will be part of x. That is, it will be a value more than 100% of x.

​

​Example.

​A store buys items at wholesale and marks the price up by 25% of x.

​0.25x

​

​The retail price will more than the original price, so it will be a value greater than 100% of x

​

​100%x + 25%x = 125% x

​1x + 0.25x = 1.25x

The retail price after a markup is more than 100%

​A store buys an item for x and marks it up by 30%.

​

​The markup equation is y=0.3x

​

​​The retail price will be (100% +30%) of x, or 130% of x.

​

​The retail price equation is y=1.3x

​