The original price of a book is 28 yuan per book. After a 20% discount, how much is each book of this kind of book?
一种图书原价每本28元，打八折后，这种图书每本多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">28 * (4/5)</gadget>
<output>112/5 = around 22.4</output>

<result>112/5 = around 22.4</result>