A project can be completed by A alone in 10 hours, B alone in 12 hours, C alone in 15 hours, A works first (1/4), how many hours will B and C cooperate to complete the rest?
一项工程，甲独做10小时完成，乙独做12小时完成，丙独做15小时完成，甲先做了(1/4)，剩下的乙、丙合作几小时完成？
<gadget id="calculator">1 / 4</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 / 12</gadget>
<output>1/12 = around 0.083333</output>

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

<gadget id="calculator">(1/12) + (1/15)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/4) / (3/20)</gadget>
<output>5</output>

<result>5</result>