The average age of Mr. Zhang, Wang Hong and Jin Ming is 17 years old; the average age of Mr. Li, Wang Hong and Jin Ming is 15 years old. Teacher Li is 27 years old this year. How old is Teacher Zhang?
张老师与王鸿和金明的平均年龄是17岁；李老师与王鸿和金明的平均年龄是15岁．李老师今年27岁，张老师今年多少岁．
<gadget id="calculator">17 * 3</gadget>
<output>51</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">45 - 27</gadget>
<output>18</output>

<gadget id="calculator">51 - 18</gadget>
<output>33</output>

<result>33</result>