A project can be completed by A and B working together in 8 days. A alone needs 12 days to complete. After working together for a few days, B will complete the rest of the project by himself, so that the time ratio between the two sections before and after B is 1:3. How many days is the actual construction period of this project?
一项工程，甲、乙两人合做8天可完成．甲单独做需12天完成．现两人合做几天后，余下的工程由乙独自完成，使乙前后两段所用时间比为1：3．这个工程实际工期为多少天？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/24) * 3</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) + (1/8)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / (1/4)</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">4 + 12</gadget>
<output>16</output>

<result>16</result>