Uncle asked Xiao Ling how old he is this year, and Xiao Ling replied: "Subtract twice my age three years ago from twice my age three years later, which is exactly my current age." How old is Xiao Ling this year?
叔叔问小灵今年年龄多大，小灵回答说："用我三年后年龄的2倍减去我三年前的年龄的2倍，正好是我现在的年龄．"小灵今年多少岁．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 + 6</gadget>
<output>12</output>

<gadget id="calculator">2 - 2</gadget>
<output>0</output>

<gadget id="calculator">1 + 0</gadget>
<output>1</output>

<gadget id="calculator">12 / 1</gadget>
<output>12</output>

<result>12</result>