A cuboid container whose length and width are both 3dm from the inside, pour 9L of water into the container, and then completely submerge a watermelon in the water (the water does not overflow), then measure the water depth in the container to be 20cm, the volume of the watermelon How many cubic decimeters?
一个长方体容器，从里面量长、宽均为3dm，向容器中倒入9L水，再把一个西瓜完全浸没在水中(水未溢出)，这时量得容器内水深为20cm，这个西瓜的体积是多少立方分米？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 - 9</gadget>
<output>9</output>

<result>9</result>