A project needs 9 days to be completed by A alone, and 12 days to be completed by B alone. Now A and B cooperate in 3 days, and B will do the rest. How many days will B need to complete?
一项工程，甲单独做需要9天完成，乙单独做需要12天完成，现由甲、乙合作3天，剩余的由乙来做，求乙需要几天可以完成？
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

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

<gadget id="calculator">(1/9) + (1/12)</gadget>
<output>7/36 = around 0.194444</output>

<gadget id="calculator">(7/36) * 3</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1 - (7/12)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">(5/12) / (1/12)</gadget>
<output>5</output>

<result>5</result>