Answer:
a. Assume that the population has a normal distribution.
b. The 90% confidence interval of the mean sale time for all homes in the neighborhood is between 219.31 days and 240.69 days.
Step-by-step explanation:
Question a:
We have to assume normality.
Question b:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
That is z with a pvalue of
, so Z = 1.645.
Now, find the margin of error M as such

In which
is the standard deviation of the population and n is the size of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 230 - 10.69 = 219.31 days.
The upper end of the interval is the sample mean added to M. So it is 230 + 10.69 = 240.69 days.
The 90% confidence interval of the mean sale time for all homes in the neighborhood is between 219.31 days and 240.69 days.
Area = (x+1) * (x+1)
Area = x^2 +2x + 1
Answer:
let the two numbers be x and y
x+y=45(equation 1)
x-y=5(equation 2)
from equation (1) y=45-x(equation 3)
substitute 45-x for y in equation 2
x-(45-x)=5
x-45+x=5
x+x-45=5
2x-45=5
2x=45+5
2x=50
x=50/2
x=25