In an open space with a length of 20 meters and a width of 15 meters, a square flower bed with a side length of 10 meters is built in the middle, and the rest is covered with lawn. How many square meters is the area of the lawn?
一块长20米、宽15米的空地，中间建一个边长10米的正方形花坛，其余铺上草坪，草坪面积是多少平方米？
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">300 - 100</gadget>
<output>200</output>

<result>200</result>