A barrel of oil has been eaten (2/7), how much is left (fill in the score).
一桶油，吃去了(2/7)，还剩多少(填分数)．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<result>5/7 = around 0.714286</result>