Now the age of the father is three times that of the son, in another 18 years the age of the father will be twice the age of the son. How old is your father now?
现在父亲的年龄是儿子的3倍，再过18年，父亲的年龄是儿子的2倍．现在父亲多少岁．
<gadget id="calculator">2 * 18</gadget>
<output>36</output>

<gadget id="calculator">36 - 18</gadget>
<output>18</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">18 / 1</gadget>
<output>18</output>

<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<result>54</result>