The elder brother has 20 pieces of chocolate, and after giving 4 pieces to the younger sister, they both have the same amount. How many pieces of chocolate did the younger sister have? (Solution of column equation)
哥哥有20块巧克力，给妹妹4块后，他们俩就一样多，妹妹原来有几块巧克力？(列方程解)
<gadget id="calculator">20 - 4 - 4</gadget>
<output>12</output>

<result>12</result>