The father is 28 years older than the son, and the mother is 23 years older than the son. The sum of the ages of the father and mother is 73 years. What is the age of the son?
父亲比儿子大28岁，母亲比儿子大23岁，父亲与母亲的年龄和是73岁，儿子的年龄是多少？
<gadget id="calculator">73 - 28 - 23</gadget>
<output>22</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">22 / 2</gadget>
<output>11</output>

<result>11</result>