The average age of the four people A, B, C, and D is 28 years old, and none of the four people is older than 30 years old, so what is the youngest possible age?
甲、乙、丙、丁四个人的平均年龄是28岁，四人中没有大于30岁的，那么年龄最小的可能是多少？
<gadget id="calculator">28 * 4</gadget>
<output>112</output>

<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">112 - 90</gadget>
<output>22</output>

<result>22</result>