The slope of the line of the equation given is -2 (by solving for y, you get y = -2x+4).
So, in order to be perpendicular, you must take the negative reciprocal.
The slope would be -1/2.
To find the absolute value remove abt negative sign in front of a number and to think of all numbers as a positive
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.
Answer:
An angle shaped as a long L is a right angle...
Step-by-step explanation: