Uncle Zhang is 45 years old. Mingming is 9 years old, how many years later, Uncle Zhang's age is 4 times of Mingming's age.
张叔叔45岁．明明9岁，多少年后，张叔叔的年龄是明明年龄的4倍．
<gadget id="calculator">45 - 9</gadget>
<output>36</output>

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

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

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<result>3</result>