Xiaofang reads a story book. She reads (3/7) of the whole book on the first day and (2/7) of the whole book on the second day. What percentage of the whole book is left unread?
晓芳读一本故事书，第一天读了全书的(3/7)，第二天读了全书的(2/7)，还剩全书的几分之几没有读？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (3/7) - (2/7)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>