A parallelogram has a base of 9 cm. If the height remains the same and the base increases by 3 cm, the area increases by 12 cm2. Find the area of the original parallelogram.
一个平行四边形，底是9厘米，如果高不变，底增加3厘米，则面积增加12平方厘米．求原来平行四边形的面积．
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>