A story book has 160 pages, read 25% of the whole book on the first day, read the remaining 20% on the second day, and read from the page number on the third day.
一本故事书160页，第一天读了全书的25%，第二天读了剩下的20%，第三天从第多少页读．
<gadget id="calculator">120 - 40</gadget>
<output>80</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 * (1/5)</gadget>
<output>16</output>

<gadget id="calculator">40 + 16 + 1</gadget>
<output>57</output>

<result>57</result>