Xiaohong bought two books at a 20% discount in the bookstore, and spent a total of 12 yuan. How much did Xiaohong save by buying these two books?
小红在书店买了两本打八折出售的书，共花了12元，小红买这两本书便宜了多少钱．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">12 / (4/5)</gadget>
<output>15</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<result>3</result>