A project can be completed in 12 days alone. If A works alone in 3 days, B will do the rest of the work, and B can complete it in another 6 days. Ask A to do 6 days alone, and B will do the rest, how many days will it take to complete?
一项工程甲独做12天完成，如果甲独做3天，余下的工作由乙去做，乙再用6天可以完成．问甲独做6天，余下的工作由乙做，还需几天才能完成？
<gadget id="calculator">6 / 12</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">3 / 12</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) / 6</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/2) / (1/8)</gadget>
<output>4</output>

<result>4</result>