Huangling Village built a 12-kilometer road. The full length (3/20) was built on the first day, the full length (3/10) was built on the second day, and the rest was completed on the third day. How many kilometers to repair?
黄岭村修一条长为12千米的公路，第一天修了全长的(3/20)，第二天修了全长的(3/10)，剩下的第三天完成，第三天修多少千米？
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">12 * (7/10)</gadget>
<output>42/5 = around 8.4</output>

<result>42/5 = around 8.4</result>