I think the better buy would be the 12-pack because the quality of the ball and the brand would determine the price. Golf balls do the same thing, you hit than lose it than buy a whole new pack of balls. The 3-pack cost less because it’s $4.95 and the 12-pack cost $18.95. By $14 much.
Answer:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the hardness of a population, and for this case we know the distribution for X is given by:
Where
and 
We are interested on this probability

And the best way to solve this problem is using the normal standard distribution and the z score given by:

If we apply this formula to our probability we got this:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
true because integers are all positive numbers, their opposites (negatives), and zero
The left-handed students12% are left handed, percent means per hundred. Change percent into per 100.
12% =

Then simplify the fraction by dividing the numerator and denominator by 4

=

=

This is the fraction showing the proportion of the left-handed students
The right-handed studentsDetermine the fraction showing the proportion of the right-handed students
1 - the left-handed
= 1 -

Equalize the denominator to 25

Simplify

This is the proportion of the right-handed students
<span>
Are there more right-handed or left-handed students?There are more right-handed students than the left-handed students, because 21/25 is more than 3/25</span>
Look up "Everything You Need To Know About Math In One Big Fat Notebook pdf." It's the best thing I've ever been given, I have it with me in math class all the time and I've aced every test. I have it with me right now and it has everything I've ever been taught about math in it so it might help you.