When digging a canal, the full length (1/6) was dug on the first day, 6.5km was dug on the second day, and the full length (2/5) was not dug. How many kilometers is the total length of this canal?
挖一条水渠，第一天挖了全长的(1/6)，第二天挖了6.5km，还剩全长的(2/5)没有挖，这条水渠全长多少千米？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/6) - (2/5)</gadget>
<output>13/30 = around 0.433333</output>

<gadget id="calculator">6.5 / (13/30)</gadget>
<output>15</output>

<result>15</result>