If the unit of a fraction added to a fraction is 1, and the unit of fraction subtracted from it is (5/7), then what is the fraction.
一个分数如果加上它的一个分数单位是1，如果减去它的一个分数单位是(5/7)，那么这个分数是多少．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

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

<gadget id="calculator">(2/7) / 2</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<result>6/7 = around 0.857143</result>