There are two engineering teams, A and B, who are repairing a 600-meter-long road. Team A repairs 20 meters a day, and team B repairs 30 meters a day. How many days will it take for the two teams to repair at the same time?
有A、B两个工程队修600米长的一条公路，A队每天修20米，B队每天修30米，他们两队同时修要几天完工？
<gadget id="calculator">20 + 30</gadget>
<output>50</output>

<gadget id="calculator">600 / 50</gadget>
<output>12</output>

<result>12</result>