Teacher Zhang and the students played the age guessing game together. Teacher Zhang said: "Multiply my age by 2, add 42, and subtract 10, it is exactly 100 years old." How old is Teacher Zhang this year?
张老师和同学们一起玩猜年龄游戏．张老师说："把我的年龄乘2，再加上42，再减去10，正好是100岁．"张老师今年多少岁．
<gadget id="calculator">10 - 42</gadget>
<output>-32</output>

<gadget id="calculator">100 + (-32)</gadget>
<output>68</output>

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

<result>34</result>