The grass on a pasture grows at a constant rate every day. This pasture can feed 15 cows for 24 days, or 20 cows for 14 days. There is a group of cows that have been eaten for six days and then two are sold, and the rest of the cows are eaten for another three days. How many cows are there in this herd?
一个牧场上的青草每天匀速生长，这片草地可供15头牛吃24天，或供20头牛吃14天．现有一群牛吃了六天后卖掉2头，余下的牛又吃了3天将草吃完．这群牛原有多少头？
<gadget id="calculator">15 * 24</gadget>
<output>360</output>

<gadget id="calculator">20 * 14</gadget>
<output>280</output>

<gadget id="calculator">360 - 280</gadget>
<output>80</output>

<gadget id="calculator">24 - 14</gadget>
<output>10</output>

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

<gadget id="calculator">15 - 8</gadget>
<output>7</output>

<gadget id="calculator">7 * 30</gadget>
<output>210</output>

<gadget id="calculator">8 * 9</gadget>
<output>72</output>

<gadget id="calculator">210 + 72</gadget>
<output>282</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">282 + 6</gadget>
<output>288</output>

<gadget id="calculator">288 / 8</gadget>
<output>36</output>

<result>36</result>