Dad, Dayong and Xiaoyong are 45 years old this year. Dad is 28 years older than Dayong, and Dayong is 4 years older than Xiaoyong. How old is Xiaoyong this year?
爸爸、大勇和小勇三人今年的年龄和是45岁，爸爸比大勇大28岁，大勇比小勇大4岁，那么今年小勇几岁？
<gadget id="calculator">28 + 4 + 4</gadget>
<output>36</output>

<gadget id="calculator">45 - 36</gadget>
<output>9</output>

<gadget id="calculator">9 / 3</gadget>
<output>3</output>

<result>3</result>