For combining like terms: it is 7z
Step-by-step explanation:

Mrs. Brown's class will earn 30 minutes of recess.
Three variable terms appear in this expression. Although 9xy has two variables, they combine to make one term.
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Answer: 
Step-by-step explanation:
The confidence interval for population mean is given by :-

, where
is the sample proportion, n is the sample size ,
is the critical z-value.
Given : Significance level : 
Sample size : n= 85
Critical value : 
Sample proportion: 
Now, the 99% confidence level will be :

Hence, the 99% confidence interval estimate of the true proportion of families who own at least one DVD player is 