To type a manuscript, it takes 8 days for A to finish typing alone, 12 days for B to finish typing alone, and 4 days for A and B to finish typing together, and B will finish the rest alone. How many days does B need to finish?
打一部书稿，甲单独打完需8天，乙单独打完需12天，甲乙合打4天后，剩下的由乙单独完成，乙需要几天才能完成？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

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

<gadget id="calculator">(1/8) + (1/12)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">(5/24) * 4</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

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

<result>2</result>