The mother is 39 years old, 5 years younger than her son, who is 4 times her age. How old is your son?
妈妈今年39岁，比儿子年龄的4倍小5岁．儿子今年多少岁？
<gadget id="calculator">39 + 5</gadget>
<output>44</output>

<gadget id="calculator">44 / 4</gadget>
<output>11</output>

<result>11</result>