The farm has a total of 3200 chickens, ducks and geese. If you sell chicken (1/3), duck (1/4), goose (1/5), there are 2400 poultry left; if you sell chicken (1/5), duck (1/4 ) and geese (1/3), there are 2320 poultry left. How many ducks are there in the farm?
养殖场有鸡、鸭、鹅三种家禽共3200只．如果卖掉鸡的(1/3)，鸭的(1/4)，鹅的(1/5)，则剩家禽2400只；如果卖掉鸡的(1/5)，鸭的(1/4)，鹅的(1/3)，则剩家禽2320只．养殖场原有鸭多少只？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/3) + (1/5)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">3_200 * (8/15)</gadget>
<output>5_120/3 = around 1_706.666667</output>

<gadget id="calculator">3_200 * 2</gadget>
<output>6_400</output>

<gadget id="calculator">6_400 - 2_400 - 2_320</gadget>
<output>1_680</output>

<gadget id="calculator">(5_120/3) - 1_680</gadget>
<output>80/3 = around 26.666667</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/5) - (1/2)</gadget>
<output>-3/10 = around -0.3</output>

<gadget id="calculator">(1/3) + (-3/10)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(80/3) / (1/30)</gadget>
<output>800</output>

<result>800</result>