Xiao Hua is 12 years old this year, Xiao Ling is 10 years old, Xiao Ming is 11 years old, and Xiao Gang is 15 years old. Four years later, what is the average age of the four of them?
今年小华12岁，小玲10岁，小明11岁，小刚15岁，四年以后，他们四人的平均年龄是多少岁？
<gadget id="calculator">12 + 4</gadget>
<output>16</output>

<gadget id="calculator">10 + 4</gadget>
<output>14</output>

<gadget id="calculator">11 + 4</gadget>
<output>15</output>

<gadget id="calculator">15 + 4</gadget>
<output>19</output>

<gadget id="calculator">16 + 14 + 15 + 19</gadget>
<output>64</output>

<gadget id="calculator">64 / 4</gadget>
<output>16</output>

<result>16</result>