The chicken farm raised 21,000 chickens this year, an increase of (2/5) compared to last year. How many chickens were raised last year?
养鸡厂今年养鸡21000只，今年比去年增加(2/5)，去年养鸡多少只？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + (2/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">21_000 / (7/5)</gadget>
<output>15_000</output>

<result>15_000</result>