The younger sister is 18 years old this year, and the older sister is 26 years old this year. When the sum of their ages is 20 years old, how old is the older sister?
妹妹今年18岁，姐姐今年26岁，当两人年龄之和是20岁时，姐姐多少岁．
<gadget id="calculator">20 + 8</gadget>
<output>28</output>

<gadget id="calculator">28 / 2</gadget>
<output>14</output>

<result>14</result>