After the 60-meter sprint event in an animal sports meeting, the chick found that the average time spent by the bear, the puppy and the rabbit was 4 minutes, while the average time spent by the bear, the puppy, the rabbit and the duckling was 5 minutes. How many minutes did the duckling spend in this game?
在一次动物运动会的60米短跑项目结束后，小鸡发现：小熊，小狗和小兔三人的平均用时为4分钟，而小熊，小狗，小兔和小鸭的平均用时为5分钟．小鸭仔这项比赛中用时多少分钟．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">20 - 12</gadget>
<output>8</output>

<result>8</result>