The perimeter of a rectangle is 42 decimeters, and the ratio of width to length is 3:4. What is the area of the rectangle?
一个长方形的周长是42分米，宽与长的比是3：4，这个长方形的面积是多少．
<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">21 * (3/7)</gadget>
<output>9</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">21 * (4/7)</gadget>
<output>12</output>

<gadget id="calculator">9 * 12</gadget>
<output>108</output>

<result>108</result>