To speed up the pace of urban construction. To make "city-better life", an engineering company undertook the task of laying an underground pipeline. If the project is laid by A engineering team alone, it will take 12 days to complete. It takes 18 days to complete the laying alone by engineering team B. Now it is decided that the two teams will construct from both ends at the same time. How many days will it take to pave?
为加快城市建设的步伐．使"城市-让生活更美好"，某工程公司承接了一地下管道的铺设任务．若该工程由甲工程队单独铺设需12天完成．由乙工程队单独铺设需18天完成．现决定由这两个队从两端同时相向施工，需要几天铺好？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/12) + (1/18)</gadget>
<output>5/36 = around 0.138889</output>

<gadget id="calculator">1 / (5/36)</gadget>
<output>36/5 = around 7.2</output>

<result>36/5 = around 7.2</result>