Xiao Miao read a 320-page story book, and read a total of 160 pages in the first 4 days. According to this calculation, how many days are left to finish reading.
小苗看一本320页的故事书，前4天一共看了160页，照这样计算，剩下的还要多少天才能看完．
<gadget id="calculator">320 - 160</gadget>
<output>160</output>

<gadget id="calculator">160 / 4</gadget>
<output>40</output>

<gadget id="calculator">160 / 40</gadget>
<output>4</output>

<result>4</result>