When the older brother's age is the younger brother's current age, the older brother's age is three times the younger brother's age. When the younger brother's age is the older brother's current age, the sum of their ages is 48. How old is the younger brother now?
当哥哥的年龄是弟弟现在的年龄时，哥哥的年龄是弟弟年龄的3倍，当弟弟的年龄是哥哥现在的年龄时，他们两人的年龄和是48，弟弟现在多少岁．
<gadget id="calculator">48 / 12</gadget>
<output>4</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<result>12</result>