There is a piece of pasture that grows at a constant rate every day, which can feed 10 cows for 12 days and 8 cows for 20 days. How many cows can be raised at most so that this piece of grass can never be eaten up?
有一片牧草每天匀速生长，可供10头牛吃12天，可供8头牛吃20天，那么最多可以养多少头牛，使得这片草永远吃不完？
<gadget id="calculator">20 * 8</gadget>
<output>160</output>

<gadget id="calculator">12 * 10</gadget>
<output>120</output>

<gadget id="calculator">160 - 120</gadget>
<output>40</output>

<gadget id="calculator">20 - 12</gadget>
<output>8</output>

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

<result>5</result>