In 2003, the annual per capita income of rural residents in western my country was about 2,800 yuan, roughly equivalent to 80% of the national per capita annual income of rural residents. How much is the national per capita annual income of rural residents?
2003年，我国西部农村居民年人均收入约为2800元，大约相当于全国农村居民人均年收入的80%，全国农村居民人均年收入约是多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2_800 / (4/5)</gadget>
<output>3_500</output>

<result>3_500</result>