Uncle Liu’s family has a rectangular nursery. If the length is increased by 10 meters, the area will increase by 640 square meters. If the width is increased by 10 meters, the area will increase by 850 square meters. What is the area of this rectangular nursery?
刘叔叔家有一个长方形苗圃，如果把它的长增加10米，面积就增加640平方米，如果把它的宽增加10米，面积就增加850平方米，这个长方形苗圃的面积是多少平方米？
<gadget id="calculator">640 / 10</gadget>
<output>64</output>

<gadget id="calculator">850 / 10</gadget>
<output>85</output>

<gadget id="calculator">64 * 85</gadget>
<output>5_440</output>

<result>5_440</result>