rectangular vegetable field is 30 meters long and 20 meters wide. Now the length of the land is increased by 20 meters and the width is increased by 10 meters. How many square meters has its area increased from the original?
一块长方形菜地，长30米，宽20米．现在这块地长增加20米，宽增加10米，它的面积比原来增加了多少平方米？
<gadget id="calculator">30 + 20</gadget>
<output>50</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">50 * 30</gadget>
<output>1_500</output>

<gadget id="calculator">30 * 20</gadget>
<output>600</output>

<gadget id="calculator">1_500 - 600</gadget>
<output>900</output>

<result>900</result>