A bunch of fruits, the first time to carry away (2/7), the second time to carry away (3/7), how much should be carried away in the third time to finish all the fruits?
一堆水果，第一次运走(2/7)，第二次运走(3/7)，第三次要运走多少才能全部运完？
<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>