Wangcun built a water canal, 8.5km was built on the first day, and 3.5km more than the first day was built on the second day. At this time, the completed canal was 4km less than the one that was not repaired. How many kilometers are left to be repaired?
王村修一条水渠，第一天修8.5km，第二天比第一天多修3.5km，这时修完的比没修的少4km，求还有多少千米没修？
<gadget id="calculator">8.5 + 3.5 + 8.5 + 4</gadget>
<output>24.5</output>

<result>24.5</result>