A job can be done by A in 9 hours and by B in 6 hours. Now A has been working for 3 hours first, and A and B will cooperate for the rest. How many hours will it take to complete the task?
一项工作，甲单独做要9小时完成，乙单独做要6小时完成．现在甲先做了3小时，剩下的由甲乙合作，还需要多少小时完成任务？
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/9) * 3</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">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/9) + (1/6)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">(2/3) / (5/18)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>