The length of a rectangle is 20 decimeters, and its width is less than its length (1/4). What is the area of this rectangle?
一个长方形的长是20分米，它的宽比长少(1/4)，这个长方形的面积是多少平方分米？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">20 * (3/4)</gadget>
<output>15</output>

<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<result>300</result>