What is the largest true fraction whose unit of fraction is (1/7).
分数单位是(1/7)的最大真分数是多少．
<gadget id="calculator">7 / 1</gadget>
<output>7</output>

<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

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