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.
First, you set your problem up like this:
-4x+3=2x-6
add 6 to both sides so it looks like this:
-4x+9=2x
add 4x to both sides so it looks like this:
9=6x
divide 6 from both sides so this is your answer:
1.5=x
Answer:
the graph has opposite x intercepts of b and -b. the graph has y intercepts at –b². the graph of the function symmetrical about the y-axis.
Step-by-step explanation:
Answer:
h = 33 hours
Step-by-step explanation:
Given that,
Addison worked 6 more hours this week than last week. In total, she worked 72 hours this week and last week.
The equation is :
2h + 6 = 72
We need to find the number of hours
2h = 72 - 6
2h = 66
h = 33
Hence, Adison worked for 33 hours last week.