There is a well from which spring water gushes out continuously, and the amount of water gushing out every minute is equal. If 3 pumps are used to pump water, the water can be pumped out in 36 minutes; if 5 pumps are used to pump water, the water can be pumped out in 20 minutes. Now it is required to pump the well water within 12 minutes, how many pumps are needed.
有一口水井，连续不断地涌出泉水，每分涌出的水量相等．如果用3台抽水机来抽水，36分可将水抽完；如果使用5台抽水机抽水，20分可将水抽完．现在要求12分内抽完井水，需要多少台抽水机．
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">36 * 3</gadget>
<output>108</output>

<gadget id="calculator">108 - 100</gadget>
<output>8</output>

<gadget id="calculator">36 - 20</gadget>
<output>16</output>

<gadget id="calculator">8 / 16</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 20</gadget>
<output>10</output>

<gadget id="calculator">100 - 10</gadget>
<output>90</output>

<gadget id="calculator">12 * (1/2)</gadget>
<output>6</output>

<gadget id="calculator">90 + 6</gadget>
<output>96</output>

<gadget id="calculator">96 / 12</gadget>
<output>8</output>

<result>8</result>