Start by adding 13 to both sides
19 = 4b-13
<span>19+13 = 4b-13+13
</span>32 = 4b
4b = 32
Then divide both sides by 4 to isolate b
4b = 32
4b/4 = 32/4
b = 8
So in the end, b = 8
Answer:
a) 
And replacing we got:

b) 
And replacing we got:

c) 
And replacing we got:

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".
Part a
Let X the random variable of interest for this case. We define the z score with the following formula:
And for this case we know that 
If we solve for x from the z score formula we got:

And replacing we got:

Part b
Let X the random variable of interest for this case. We define the z score with the following formula:
And for this case we know that 
If we solve for x from the z score formula we got:

And replacing we got:

Part c
Let X the random variable of interest for this case. We define the z score with the following formula:
And for this case we know that 
If we solve for x from the z score formula we got:

And replacing we got:

Since we have (4,?) we know x=4. Substitute this into the equation and solve for y.
y= 2/7*4+3
y= 2/7*4/1+3
y= 8/7+3
y= 8/7 + 3/1
y= 16/14 + 42/14
y= 58/14 or 4.14
Answer:15
Step-by-step explanation: