This year, my father's age is three times that of Xiaofang's. A few years ago, my father's age was five times that of Xiaofang's. A few years ago, my father's age was seven times that of Xiaofang's. Their age difference is between 20 and 30 years old. How old is Dad?
今年爸爸的年龄是小芳年龄的3倍，几年前，爸爸的年龄是小芳年龄的5倍，再几年前，爸爸的年龄是小芳年龄的7倍．他们的年龄差在20岁至30岁之间，爸爸今年多少岁．
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 + 24</gadget>
<output>36</output>

<result>36</result>