This year the son's age is the father's age (1/4), and 15 years later, the son's age is the father's age (5/11). How old is your son this year?
今年儿子的年龄是父亲年龄的(1/4)，15年后，儿子的年龄是父亲年龄的(5/11)．今年儿子多少岁．
<gadget id="calculator">5 / 11</gadget>
<output>5/11 = around 0.454545</output>

<gadget id="calculator">15 * (5/11)</gadget>
<output>75/11 = around 6.818182</output>

<gadget id="calculator">15 - (75/11)</gadget>
<output>90/11 = around 8.181818</output>

<gadget id="calculator">4 * (5/11)</gadget>
<output>20/11 = around 1.818182</output>

<gadget id="calculator">(20/11) - 1</gadget>
<output>9/11 = around 0.818182</output>

<gadget id="calculator">(90/11) / (9/11)</gadget>
<output>10</output>

<result>10</result>