pool is equipped with a water inlet pipe and several same outlet pipes (the water inlet pipe and the water outlet pipe are different), first open the water inlet pipe and wait for the pool to have some water, and then open the water outlet pipe, if you open a water outlet pipe, after 12 minutes, the pool will Empty; if two outlet pipes are opened at the same time, and the pool is empty after 4 minutes, then how many minutes later are the outlet pipes opened than the inlet pipes?
一个水池装有一根进水管和若干根同样的出水管(进水管和出水管不同)，先打开进水管等水池有了一些水后，再打开出水管，如果打开一个出水管，12分钟后水池空；如果同时打开2个出水管，4分钟后水池空，那么，出水管比进水管晚开几分钟？
<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">24 - 12</gadget>
<output>12</output>

<result>12</result>