A project is done separately, A takes 20 days, B takes 30 days, and C takes 12 days. If A and B work together for 2 days first, how many days will it take for C to do the rest?
一项工程单独做，甲要20天，乙要30天，丙要12天．如果甲、乙先合做2天，剩下的由丙做还要多少天？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">2 * (1/12)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

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

<gadget id="calculator">(5/6) / (1/12)</gadget>
<output>10</output>

<result>10</result>