Someone asked the child's age and replied: "9 years younger than half the age of the father." Asked the age of the father again and replied: "2 years more than four times the age of the child." How old is the child.
有人问孩子年龄，回答："比爸爸的岁数的一半少9岁．"又问爸爸的年龄，回答说："比孩子的4倍多2岁．"孩子年龄多少岁．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 2</gadget>
<output>1</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">(1/2) * 4</gadget>
<output>2</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<result>8</result>