Answer: 
Step-by-step explanation:
The confidence interval for population mean is given by :-

Given : Sample size :
, which is a large sample , so we apply z-test .
Sample mean : 
Standard deviation : 
Significance level : 
Critical value : 
Now, a confidence interval at the 95% level of confidence will be :-

Answer:
60
Step-by-step explanation:
Because 7.7^2 equals 60,
5x - 4y = 7
x = 5 - y
5(5 - y) - 4y = 7
25 - 5y - 4y = 7
-5y - 4y = 7 - 25
-9y = - 18
y = -18/-9
y = 2 <== y coordinate is 2
If -15 is equal to -0.2x, then 15/0.2=75
x=75