Print a manuscript, if A and B cooperate to complete it in 6 hours, if B and C cooperate to complete it in 9 hours, if A and C cooperate to complete it in 18 hours. How many hours does it take for A, B, and C to finish playing together?
打印一份稿件，若甲乙合作6小时打完，若乙丙合作9小时完成，若甲丙合作18小时完成．现在甲乙丙三人合作需几小时打完？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

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

<gadget id="calculator">(1/6) + (1/9) + (1/18)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 2</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>