batch of parts can be completed in 12 days by A alone, 24 days by B alone, how many days will the two work together to complete.
一批零件，甲单独做12天完成，乙单独做24天完成，两人合作多少天完成．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/12) + (1/24)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / (1/8)</gadget>
<output>8</output>

<result>8</result>