A rope is (4/5) meters long, cut off (1/7) of this rope for the first time, and cut off (3/7) of this rope for the second time. How much of this rope is left?
一条绳子长(4/5)米，第1次剪去这条绳子的(1/7)，第二次剪去这条绳子的(3/7)．这条绳子还剩几分之几？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (1/7) - (3/7)</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>