The length of a rectangle is 20 decimeters, and its width is 5 decimeters more than that. What is the area of this rectangle?
一个长方形长20分米，比宽多5分米，这个长方形的面积是多少？
<gadget id="calculator">20 - 5</gadget>
<output>15</output>

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

<result>300</result>