Xiaohua reads a storybook, read it on the first day (2/7), and read it on the second day (4/7), how much of it is left?
小华看一本故事书，第一天看了它的(2/7)，第二天看了它的(4/7)，还剩下几分之几没有看？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(2/7) + (4/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">1 - (6/7)</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>