The father is 45 years old and the son is 23 years old. How many years ago was the father twice the age of the son?
父亲45岁，儿子23岁．多少年前父亲年龄是儿子的2倍？
<gadget id="calculator">45 - 23</gadget>
<output>22</output>

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

<gadget id="calculator">22 / 1</gadget>
<output>22</output>

<gadget id="calculator">23 - 22</gadget>
<output>1</output>

<result>1</result>