The sum of the ages of Xiao Ming and Xiao Gang is 33 years old, the sum of the ages of Xiao Gang and Xiao Liang is 28 years old, and the sum of the ages of Xiao Ming and Xiao Liang is 29 years old. What is the average age of Xiao Ming, Xiao Gang, and Xiao Liang?
小明和小刚的年龄和是33岁，小刚和小亮的年龄和是28岁，小明和小亮的年龄和是29岁．小明、小刚、小亮三人的平均年龄是多少岁？
<gadget id="calculator">33 + 28 + 29</gadget>
<output>90</output>

<gadget id="calculator">90 / 2 / 3</gadget>
<output>15</output>

<result>15</result>