Let x represent the original price. Given that every item in the store is advertised as one- fourth off the original price, it means that the amount taken off the sale price is 1/4 * x = x/4
Since it is removed off the original price, the sale price of an item would be
x - x/4 = 3x/4
If an item is marked with a sale price of 90, it means that
3x/4 = 90
3x = 90 * 4 = 360
x = 360/3
x = 120
The original price is 120