job can be done by A alone in 9 days and B by himself in 12 days. Now the two are working together, and B asks for a few days off due to some business, so the whole work can only be completed in 6 days, how many days does B ask for leave?
一项工作，甲单独做9天可以完成，乙单独做12天可以完成．现在二人合作，乙因事请假几天，所以整个工作6天才能完成，乙请假几天？
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/9) * 6</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(1/12) * 6</gadget>
<output>1/2 = around 0.5</output>

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

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

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

<result>2</result>