To process a pile of rice, A thresher alone can complete it in 8 hours, and B thresher alone can complete it in 6 hours. If A thresher does it for 2 hours first, then B thresher does it alone. How many hours will it take for B thresher to complete?
加工一堆稻谷，甲脱粒机单独做8小时完成，乙脱粒机单独做6小时完成．如果甲脱粒机先做2小时，再由乙脱粒机单独做．乙脱粒机还要几小时才能完成？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) * 2</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">(3/4) / (1/6)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>