To build a road, the length that has been repaired accounts for the length that has not been repaired (7/13), and the length that has not been repaired accounts for the total length.
修一条公路，已修的长度占未修的(7/13)，未修的长度占全长的多少．
<gadget id="calculator">7 / 13</gadget>
<output>7/13 = around 0.538462</output>

<gadget id="calculator">1 + (7/13)</gadget>
<output>20/13 = around 1.538462</output>

<gadget id="calculator">1 / (20/13)</gadget>
<output>13/20 = around 0.65</output>

<result>13/20 = around 0.65</result>