A is 49 years old this year, and B is 16 years old this year. How many years ago, A's age was 4 times that of B's.
甲今年49岁，乙今年16岁，多少年前甲的年龄是乙的4倍．
<gadget id="calculator">49 - 16</gadget>
<output>33</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">33 / 3</gadget>
<output>11</output>

<gadget id="calculator">16 - 11</gadget>
<output>5</output>

<result>5</result>