The student asked the teacher how old he was, and the teacher said: "When I was your age, you were just 3 years old; when you were my age, I was already 39 years old." How old is the teacher?
学生问老师多少岁，老师说："当我象你这么大时，你刚3岁；当你象我这么大时，我已经39岁了．"老师的年龄是多少岁．
<gadget id="calculator">39 - 3</gadget>
<output>36</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">36 / 3</gadget>
<output>12</output>

<gadget id="calculator">39 - 12</gadget>
<output>27</output>

<result>27</result>