The x-coord. of the vertex is halfway between the given zeros. Here, it'd be halfway between x=3 and x=9, which comes out to x = 6 (answer).
Step-by-step explanation:

Answer: Two-tailed test.
Population mean is the parameter which is tested.
Step-by-step explanation:
Given : 

We know that , the alternative hypothesis (
) indicates kind of the hypothesis test we need to perform whether left-tailed, right-tailed, or two-tailed.
Here, the alternative hypothesis (
) is two-tailed, so the hypothesis test is a two-tailed test.
Also, the parameter present in the hypothesis is
which is a symbol to represent the population mean.
Thus , Population mean is the parameter which is tested.
Yes it is it's been that way for years
Since the painting is hung in center of a rectangular wall ,the distance between them on either side will be the same.so we can divide the length of the painting and wall by 2.we will get 2.4/2=1.2 feet and 20/2=10 feet .10-1.2=8.8 feet gives the distance between the right edge of the painting and right edge of the wall