A project alone takes 6 hours, and B alone takes 8 hours. If A and B cooperate, the efficiency will be reduced by 1/7. How many hours will it take for A and B to cooperate?
一件工程，甲单独做需要6小时，乙单独做需要8小时，若甲乙合作，则效率都要降低原来的(1/7)，那甲乙合作需要多少小时．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/6) + (1/8)</gadget>
<output>7/24 = around 0.291667</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">(7/24) * (6/7)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / (1/4)</gadget>
<output>4</output>

<result>4</result>