There is a pool equipped with a water inlet pipe and a drain pipe. The water inlet pipe alone can fill a pool of water in 12 hours. If the two pipes are opened at the same time, only 1/3 of the pool can be filled in 8 hours. How long does it take to open the drain pipe alone? Can you drain half of the pool?
有一水池装有进水管和排水管，单开进水管12小时可以注满一池水，如果同时开放两管，8小时只能注满水池的(1/3)，问单开排水管，几小时可以把半池水排完？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 8</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/12) - (1/24)</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/2) / (1/24)</gadget>
<output>12</output>

<result>12</result>