The purchase price of a book is 8 yuan, the selling price is 12 yuan, and the profit is 160 yuan when it is sold (4/5). How many books are there in total?
一本书进价8元，售价12元，卖出(4/5)时赚了160元，问一共有多少本．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">160 / (4/5) / 4</gadget>
<output>50</output>

<result>50</result>