A piece of grass grows green grass at a uniform rate every day. It can feed 24 cows for 6 days and 20 cows for 10 days. How many cows can eat for 12 days?
一片草地，每天都匀速长出青草，可供24头牛吃6天，也可供20头牛吃10天，这片草地可供多少头牛吃12天．
<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<gadget id="calculator">24 * 6</gadget>
<output>144</output>

<gadget id="calculator">200 - 144</gadget>
<output>56</output>

<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<gadget id="calculator">56 / 4</gadget>
<output>14</output>

<gadget id="calculator">14 * 10</gadget>
<output>140</output>

<gadget id="calculator">200 - 140</gadget>
<output>60</output>

<gadget id="calculator">14 * 12</gadget>
<output>168</output>

<gadget id="calculator">60 + 168</gadget>
<output>228</output>

<gadget id="calculator">228 / 12</gadget>
<output>19</output>

<result>19</result>