The elder sister's current age is four times the younger brother's age at that time. The elder sister's age at that time was the same as the younger brother's current age. The sum of the elder sister's and younger brother's current ages is 26. What is the younger brother's current age?
姐姐现在的年龄是弟弟当年年龄的4倍，姐姐当年的年龄和弟弟现在的年龄相同，姐姐与弟弟现在的年龄和为26岁，则弟弟现在的年龄是多少岁．
<gadget id="calculator">26 + 26</gadget>
<output>52</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + 1 + 1 + (1/4)</gadget>
<output>13/4 = around 3.25</output>

<gadget id="calculator">52 / (13/4)</gadget>
<output>16</output>

<gadget id="calculator">26 - 16</gadget>
<output>10</output>

<result>10</result>