There is a job, A does it for 2 days, B continues to do it, and after 10 days, the job is completed. Given that it takes 30 days for B to complete the task alone, how many days will it take for A to complete the task alone?
有一工作，甲做2天后乙接着做，做了10天后完成了工作．已知乙单独完成需要30天，那么甲单独完成此工作需要多少天．
<gadget id="calculator">10 / 30</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 + 10</gadget>
<output>12</output>

<gadget id="calculator">(2/3) / 12</gadget>
<output>1/18 = around 0.055556</output>

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

<result>18</result>