A completes (1/3) of a certain project in 5 hours, B completes (1/5) of this project in 4 hours, and C completes (1/4) of this project in 3 hours. If B alone does 2 Hours, the remaining work will be completed by A, B, and C together, how many hours will it take?
甲用5小时完成某项工程的(1/3)，乙用4小时完成此项工程的(1/5)，丙用3小时完成此项工程的(1/4)，如果乙单独干2小时，余下的工作由甲、乙、丙共同完成，还需要多少小时．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / 4</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 2</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 5</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / 3</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/15) + (1/20) + (1/12)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(9/10) / (1/5)</gadget>
<output>9/2 = around 4.5</output>

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