A rectangular vegetable field is 20m long and long (4/5) wide, what is the area of the vegetable field
一块长方形菜地，长20m，宽是长的(4/5)，则菜地的面积为多少
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5)</gadget>
<output>16</output>

<gadget id="calculator">20 * 16</gadget>
<output>320</output>

<result>320</result>