The ratio of the areas of rooms A and B is 3:5, the area of room B is 20 square meters, what is the area of room A in square meters?
甲、乙两个房间的面积比是3：5，乙房间的面积是20平方米，甲房间的面积是多少平方米．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">20 * (3/5)</gadget>
<output>12</output>

<result>12</result>