There are 2,400 chickens, ducks, and geese in the farm. The number of chickens is the sum of the number of ducks and geese (2/3), and the number of ducks is the sum of the number of chickens and geese (1/2). How many geese are there in the farm?
饲养场养的鸡、鸭、鹅共2400只，鸡的只数是鸭和鹅只数和的(2/3)，鸭的只数是鸡和鹅只数和的(1/2)，饲养场养的鹅有多少只？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (2/5) - (1/3)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">2_400 * (4/15)</gadget>
<output>640</output>

<result>640</result>