A batch of parts, A and B work together in 12 days to complete. After they worked together for several days, B asked for leave due to business, and B only completed (3/10) of the total task at this time. A continued to do it, and it took 14 days from the beginning to the completion of the task. May I ask: How many days did A work alone?
一批零件，甲、乙合做12天完成．他们合做若干天后，乙因事请假，乙这时只完成了总任务的(3/10)．甲继续做，从开始到完成任务用了14天．请问：甲单独做了几天？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) / 14</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) - (1/20)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(3/10) / (1/30)</gadget>
<output>9</output>

<gadget id="calculator">14 - 9</gadget>
<output>5</output>

<result>5</result>