A project can be completed in (1/6) hours alone, and B can be completed in (1/7) hours alone. If A and B work together, how many hours can they be completed?
一项工程，甲单独做(1/6)小时完成，乙单独做(1/7)小时完成，如果甲乙合做，多少小时能完成．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

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

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

<gadget id="calculator">1 / (1/7)</gadget>
<output>7</output>

<gadget id="calculator">6 + 7</gadget>
<output>13</output>

<gadget id="calculator">1 / 13</gadget>
<output>1/13 = around 0.076923</output>

<result>1/13 = around 0.076923</result>