For a document, it takes 8 hours for A and B to type together, and it takes 12 hours for A to type alone. How many hours does it take for B to finish typing alone?
一份文件，甲、乙合打8小时完成，甲单独打要12小时完成．乙单独打要几小时完成？
<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>1/24 = around 0.041667</output>

<gadget id="calculator">1 / (1/24)</gadget>
<output>24</output>

<result>24</result>