job is completed in 9 days by teams A and B, by teams B and C in 12 days, by teams A and C in 18 days, how many days will it take for the three teams to complete it now?
一项工作，甲乙两队合作9天完成，乙丙两队合作12天完成，甲丙两队合作需18天完成，现在三队合作需多少天完成．
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<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">(1/9) + (1/12) + (1/18)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / 2</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / (1/8)</gadget>
<output>8</output>

<result>8</result>