This year, the average age of Xiao Ming, father, and mother is 29 years old. It is known that the average age of father and mother is 37 years old. How old is Xiao Ming this year?
今年，小明、爸爸、妈妈的平均年龄为29岁，已知爸爸和妈妈两人的平均年龄是37岁，小明今年多少岁．
<gadget id="calculator">29 * 3</gadget>
<output>87</output>

<gadget id="calculator">37 * 2</gadget>
<output>74</output>

<gadget id="calculator">87 - 74</gadget>
<output>13</output>

<result>13</result>