The department store sells logo t-shirts at an original price of $12.50. Every month that a t-shirt doesn’t sell, the store reduces the price by 25%. Brianna calculated the price after two reductions:

12 dollars and 50 cents minus (12 dollars and 50 cents) (0.25) minus (12 dollars and 50 cents) (0.25) = 6 dollars and 25 cents

What is Brianna’s error?