A road has been repaired 2km less than the full length (13/20), and there is still 9km to be repaired. How long is this road in kilometers?
一条路，已经修的比全长的(13/20)少2km，还有9km没有修．这条路全长多少千米？
<gadget id="calculator">9 - 2</gadget>
<output>7</output>

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

<gadget id="calculator">1 - (13/20)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">7 / (7/20)</gadget>
<output>20</output>

<result>20</result>