能帮我翻译一下吗consider an urn containing 12 balls,of which 8 are white.A sample of size 4 is to be drawn with replacement (without replacement).what is the conditional probability(in each case) that the first and third balls drawn will be white given that the sample drawn contains exactly 3 white balls?第二题an urn initially contains white and 7 black balls,each time a ball is selected,its color is noted and it is replaced in the urn along with 2 other balls of the same color, pute the probability that : 英语
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【答案】 假设一个urn（瓮）中有12个球,其中8个白色的.大小为4的样品被画上其他颜色（或者没有）,假设被画样品只有3个白色的球,那么第一个和第三个球被画成白色的概率（在每种情况下）是多少?
urn（瓮）罪作出有白色和7个黑色球,每次选中一个球,记下颜色,然后同翁中2个其他相同颜色的球一起在翁中被替换,计算概率：