A project can be completed by team A alone in 18 days. If team A works in 3 days and team B works in 4 days, it can complete half of the project. If it is found that the time spent in the two sections is equal after completion, how many days will it take to complete the project?
一件工程，甲队独做18天可以完成，若甲队做3天乙队做4天恰好可完成工程的一半，现在甲、乙两队合做若干天以后，再由乙队单独完成，做完后发现两段所用的时间相等，则完成工程共用多少天？
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

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

<gadget id="calculator">(1/18) + (1/12) + (1/12)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 / (2/9)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) * 2</gadget>
<output>9</output>

<result>9</result>