A project is completed in 9 days by teams A and B, and by teams B and C in 12 days. Now teams A and B have worked together for 3 days, and then teams B and C have worked together for 6 days , Finally, Team C completed the entire project in 12 days alone. How many days will it take for the entire project to be completed by teams A and C?
一项工程，甲、乙两队合做9天完成，乙、丙两队合做12天完成，现在甲、乙两队合做了3天，接着乙、丙两队又合做了6天，最后由丙队单独12天完成了整个工程．如果整个工程由甲、丙两队合做需要几天完成？
<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">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) / 12</gadget>
<output>1/72 = around 0.013889</output>

<gadget id="calculator">(1/12) - (1/72)</gadget>
<output>5/72 = around 0.069444</output>

<gadget id="calculator">(1/9) - (5/72)</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/24) + (1/72)</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">1 / (1/18)</gadget>
<output>18</output>

<result>18</result>