A cable is laid between A and B. When (4/7) of the entire project is completed, it is exactly 5 kilometers beyond the midpoint. How many kilometers of cables are still left to be laid?
在甲乙两地之间铺设电缆，当完成了全部工程的(4/7)时，恰好超过中点5千米，还有多少千米电缆没有铺设．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/7) - (1/2)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">5 / (1/14)</gadget>
<output>70</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">70 * (3/7)</gadget>
<output>30</output>

<result>30</result>