Xiaohong reads a book, the first day (2/7), and the second day (3/7), how many books are left?
小红看一本书，第一天看了(2/7)，第二天看了(3/7)，还剩多少没有看？
<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">(2/7) + (3/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

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