The father is 38 years old this year, and the son is 8 years old this year. How many years later, the father's age will be 2.5 times the son's age.
爸爸今年38岁，儿子今年8岁，多少年后爸爸的年龄是儿子年龄的2.5倍．
<gadget id="calculator">38 - 8</gadget>
<output>30</output>

<gadget id="calculator">2.5 - 1</gadget>
<output>1.5</output>

<gadget id="calculator">30 / 1.5</gadget>
<output>20</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<result>12</result>