Xiao Gang used a 14-meter fence to form a rectangular chicken pen with a width of 3.5 meters. What is its area in square meters.
小刚用14米篱笆靠一面墙围成一个宽3.5米的长方形养鸡栏．它的面积是多少平方米．
<gadget id="calculator">3.5 * 2</gadget>
<output>7</output>

<gadget id="calculator">14 - 7</gadget>
<output>7</output>

<gadget id="calculator">7 * 3.5</gadget>
<output>24.5</output>

<result>24.5</result>