A workshop originally had a total of 84 kg of zinc and copper. Now it is necessary to add 12 kg of copper to cast zinc and copper into an alloy at a ratio of 1:2. How many kilograms of original copper?
某车间原有锌和铜共84千克，现在要把锌和铜按1：2熔铸成一种合金，需要添加12千克铜．原有铜多少千克？
<gadget id="calculator">84 + 12</gadget>
<output>96</output>

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

<gadget id="calculator">96 / 3</gadget>
<output>32</output>

<gadget id="calculator">84 - 32</gadget>
<output>52</output>

<result>52</result>