When Wang Bin reads a book, he reads the whole book (3/7) on the first day, and (1/7) the whole book on the second day. How much of the book is left?
王彬看一本书，第一天看了全书的(3/7)，第二天看了全书的(1/7)．还剩下全书的几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

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

<gadget id="calculator">1 - (3/7) - (1/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(3/7) + (1/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>