A pond is going to be drained completely, but at the same time, water flows into the pond at a constant speed. If 8 pumps are used, it can be drained in 10 days; if 6 pumps are used, it can be drained in 20 days. Question: If the water needs to be drained in 5 days, how many identical water pumps are needed to pump water?
现欲将一池塘水全部抽干，但同时有水匀速流入池塘．若用8台抽水机10天可以抽干；用6台抽水机20天能抽干．问：若要5天抽干水，需多少台同样的抽水机来抽水？
<gadget id="calculator">6 * 20</gadget>
<output>120</output>

<gadget id="calculator">8 * 10</gadget>
<output>80</output>

<gadget id="calculator">120 - 80</gadget>
<output>40</output>

<gadget id="calculator">20 - 10</gadget>
<output>10</output>

<gadget id="calculator">40 / 10</gadget>
<output>4</output>

<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<gadget id="calculator">40 / 5</gadget>
<output>8</output>

<gadget id="calculator">4 + 8</gadget>
<output>12</output>

<result>12</result>