The chicken farm raised 3600 chickens this year, an increase of (2/7) compared to last year. How many chickens were raised last year?
养鸡厂今年养鸡3600只，比去年增加了(2/7)，去年养鸡多少只．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 + (2/7)</gadget>
<output>9/7 = around 1.285714</output>

<gadget id="calculator">3_600 / (9/7)</gadget>
<output>2_800</output>

<result>2_800</result>