Xiao Ming is 15 years old and Hong Hong is 17 years old. What is their average age?
小明15岁，红红17岁，两人的平均年龄是多少岁．
<gadget id="calculator">15 + 17</gadget>
<output>32</output>

<gadget id="calculator">32 / 2</gadget>
<output>16</output>

<result>16</result>