For an extra-curricular book, Xiao Ming read (2/7) of this book on the first day and (3/7) of this book on the second day, and what percentage of this book did not read?
一本课外书，小明第一天看了这本书的(2/7)，第二天看了这本书的(3/7)，还有这本书的几分之几没有看？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

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

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