Xiaoxiao read a 280-page story book. I read (1/4) of the whole book on the first day and (1/7) of the whole book on the second day. How many pages are left?
笑笑阅读一本280页的故事书，第一天读了全书的(1/4)，第二天读了全书的(1/7)，还剩下多少页没有读完？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/4) - (1/7)</gadget>
<output>17/28 = around 0.607143</output>

<gadget id="calculator">280 * (17/28)</gadget>
<output>170</output>

<result>170</result>