It takes two students A and B to make an airplane model together in 4 hours, A alone takes 6 hours to complete, and B alone takes how many hours to complete.
甲、乙两位同学一起做一架飞机模型要四小时完成，甲单独做要6小时完成，乙单独做要多少小时完成．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/4) - (1/6)</gadget>
<output>1/12 = around 0.083333</output>

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

<result>12</result>