The average age of Zhang Wei's father and mother is 34 years old. If Zhang Wei is included, the average age of their family of three is 26 years old. How old is Zhang Wei this year?
张伟的爸爸和妈妈的平均年龄是34岁，如果把张伟也算进去，他们一家三口的平均年龄是26岁，张伟今年几岁了？
<gadget id="calculator">26 * 3</gadget>
<output>78</output>

<gadget id="calculator">34 * 2</gadget>
<output>68</output>

<gadget id="calculator">78 - 68</gadget>
<output>10</output>

<result>10</result>