Xiao Ming's age this year is his father's age (1/5). After 12 years, Xiao Ming's age will be his father's (3/7). How old is Xiao Ming this year?
小明今年的年龄是爸爸年龄的(1/5)，12年后，小明的年龄将是爸爸的(3/7)，小明今年多少岁．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">12 * (3/7)</gadget>
<output>36/7 = around 5.142857</output>

<gadget id="calculator">12 - (36/7)</gadget>
<output>48/7 = around 6.857143</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/7) - (1/5)</gadget>
<output>8/35 = around 0.228571</output>

<gadget id="calculator">(48/7) / (8/35)</gadget>
<output>30</output>

<gadget id="calculator">30 * (1/5)</gadget>
<output>6</output>

<result>6</result>