To welcome the "Children's Day" Children's Day, all books in the children's counter of the Book Building will be sold at a 20% discount. "20% off", a set of "Children's Encyclopedia" is originally priced at 65 yuan, how much cheaper it is after the discount.
迎接"六一"儿童节，图书大厦少儿专柜所有图书打八折出售，"八折"，一套《少儿百科全书》原价65元，打折后便宜了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">65 * (4/5)</gadget>
<output>52</output>

<gadget id="calculator">65 - 52</gadget>
<output>13</output>

<result>13</result>