Two tunnel engineering teams jointly opened a tunnel with a length of 222.6 meters. The first team excavated 12.6 meters per day, and the second team excavated 15.4 meters per day. Team 1 starts working in advance, and the two teams start to cooperate the next day. How many days will it take to open?
两个隧道工程队同开一条长222.6米的隧道，1队每天开凿12.6米，2队每天开凿15.4米．1队提前开始工作，第二天两队开始合作，再用几天可以开通？
<gadget id="calculator">222.6 - 12.6</gadget>
<output>210</output>

<gadget id="calculator">12.6 + 15.4</gadget>
<output>28</output>

<gadget id="calculator">210 / 28</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>