The pasture is full of grass and can feed 27 cows for 6 weeks, or 23 cows for 9 weeks. If the grass grows evenly every week. How many cows can eat for a week with the original amount of grass?
牧场上长满了草，可供27头牛吃6周，或可供23头牛吃9周．如果牧草每周均匀地生长．问原有草量可供几头牛吃一周？
<gadget id="calculator">27 * 6</gadget>
<output>162</output>

<gadget id="calculator">23 * 9</gadget>
<output>207</output>

<gadget id="calculator">207 - 162</gadget>
<output>45</output>

<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">45 / 3</gadget>
<output>15</output>

<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">162 - 90</gadget>
<output>72</output>

<gadget id="calculator">72 + 15</gadget>
<output>87</output>

<gadget id="calculator">87 / 1</gadget>
<output>87</output>

<result>87</result>