There is a project, it takes 18 days for A and B to cooperate, 12 days for B and C to cooperate, and 15 days for A and C to complete. If B and C cooperate for 5 days, and then A alone completes the remaining work, how many days does A need to do?
有一项工程，甲、乙合作需要18天，乙、丙合作需要12天，甲、丙合作需要15天完成．如果乙、丙合作5天，再由甲单独完成剩下的工作，那么甲还需要做多少天？
<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">1 - (5/12)</gadget>
<output>7/12 = around 0.583333</output>

<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 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/18) + (1/12) + (1/15)</gadget>
<output>37/180 = around 0.205556</output>

<gadget id="calculator">(37/180) / 2</gadget>
<output>37/360 = around 0.102778</output>

<gadget id="calculator">(37/360) - (1/12)</gadget>
<output>7/360 = around 0.019444</output>

<gadget id="calculator">(7/12) / (7/360)</gadget>
<output>30</output>

<result>30</result>