Xiaohong is 7 years old, Xiaoli is 8 years old, Xiaolan is 5 years old, Xiaogang and Xiaoli are the same age, what is their average age?
小红7岁，小丽8岁，小兰5岁，小刚和小丽同岁，他们的平均年龄是多少岁．
<gadget id="calculator">7 + 8 + 5 + 8</gadget>
<output>28</output>

<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<result>7</result>