One job can be done by A alone in 12 hours, B by himself in 10 hours, and C by himself in 15 hours. Now A will do the work for 2 hours first, and B and C will do the rest together. How many hours will it take to complete?
一件工作，甲单独做12小时完成，乙单独做10小时完成，丙单独做15小时完成．现在甲先做2小时后，余下的由乙丙二人合做，还需几小时才能完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 2</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

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

<result>5</result>