Three years ago, the younger brother's age was the older brother's (1/5), and this year the younger brother's age is the older brother's (1/2), so how old is the older brother this year?
三年前弟弟的年龄是哥哥的(1/5)，今年弟弟年龄是哥哥的(1/2)，则哥哥今年多少岁．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 * (1/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">3 - (3/5)</gadget>
<output>12/5 = around 2.4</output>

<gadget id="calculator">2 * (1/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(12/5) / (3/5)</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>