book has 320 pages. Xiaogang read 19% of the whole book on the first day and 31% of the whole book on the second day. How many pages are left?
一本书有320页，小刚第一天看了全书的19%，第二天看了全书的31%，还剩多少页没有看？
<gadget id="calculator">19 / 100</gadget>
<output>19/100 = around 0.19</output>

<gadget id="calculator">31 / 100</gadget>
<output>31/100 = around 0.31</output>

<gadget id="calculator">1 - (19/100) - (31/100)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">320 * (1/2)</gadget>
<output>160</output>

<result>160</result>