A rectangular piece of land, if the length is reduced by 5 meters, the area will be reduced by 200 square meters; if the width is increased by 4 meters, the area will be increased by 320 square meters. What is the area of the land in square meters?
一块长方形的地，如果长减少5米，面积就减少200平方米；如果宽增加4米，面积就增加320平方米．这块地的面积是多少平方米？
<gadget id="calculator">320 / 4</gadget>
<output>80</output>

<gadget id="calculator">200 / 5</gadget>
<output>40</output>

<gadget id="calculator">80 * 40</gadget>
<output>3_200</output>

<result>3_200</result>