The height of a parallelogram is 10 decimeters. If the base remains unchanged and the height increases by 12 decimeters, the area increases by 84 square decimeters. What is the original area of the parallelogram?
一个平行四边形的高是10分米，如果底不变，高增加12分米，面积就增加84平方分米，这个平行四边形原来的面积是多少平方分米？
<gadget id="calculator">84 / 12</gadget>
<output>7</output>

<gadget id="calculator">7 * 10</gadget>
<output>70</output>

<result>70</result>