For a project, it takes 35 hours for A to do it alone, and 2/5 of the whole project can be completed by B alone for 10 hours. How many hours will it take for the remaining two to cooperate?
一项工程，甲独做需35小时，乙独做10小时可完成全部工程的(2/5)，余下的两人合作，还要几小时？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 35</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(2/5) / 10</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(1/35) + (1/25)</gadget>
<output>12/175 = around 0.068571</output>

<gadget id="calculator">(3/5) / (12/175)</gadget>
<output>35/4 = around 8.75</output>

<result>35/4 = around 8.75</result>