A project is completed by Team A in 12 days alone, and Team B in 18 days alone. Now the two teams are working together, and A is away for a few days in the middle, and it is finally completed in 9 days. How many days is Team A away in the middle?
一件工程，由甲队独做12天完成，乙队独做18天完成，现在两队合作中途甲离开了几天，最后经过9天完成，那么中途甲队离开了几天？
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/18) * 9</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) / (1/12)</gadget>
<output>6</output>

<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<result>3</result>