This year the father is 27 years older than the son, and 3 years later the father will be 4 times as old as the son, so how old is the son this year?
今年父亲比儿子大27岁，3年后父亲的年龄是儿子的4倍，那么儿子今年多少岁．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<result>6</result>