A bookshop has a sale.
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Answer:
The desired z-score is 2.
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
n(12,2.5)
This means that
z score when x =17
This is Z when X = 17. So
The desired z-score is 2.
3 - 
= 
- 7
First, simplify
to 
/ Your problem should look like: 3 - = - 7
Second, simplify to 
/ Your problem should look like: 3 - = - 7
Third, multiply both sides by 9 (the LCD of 9,3). / Your problem should look like: 27 - 2b = 3b - 63
Fourth, add 2b to both sides. / Your problem should look like: 27 = 3b - 63 + 2b
Fifth, simplify 3b - 63 + 2b to 5b - 63. / Your problem should look like: 27 = 5b - 63
Sixth, add 63 to both sides. / Your problem should look like: 27 + 63 = 5b
Seventh, simplify 27 + 63 to 90. / Your problem should look like: 90 = 5b
Eighth, divide both sides by 5. / Your problem should look like:
= b
Ninth, simplify to 18. / Your problem should look like: 18 = b
Tenth, switch sides. Your problem should look like: b = 18
Answer: b = 18
First, simplify
Second, simplify
Third, multiply both sides by 9 (the LCD of 9,3). / Your problem should look like: 27 - 2b = 3b - 63
Fourth, add 2b to both sides. / Your problem should look like: 27 = 3b - 63 + 2b
Fifth, simplify 3b - 63 + 2b to 5b - 63. / Your problem should look like: 27 = 5b - 63
Sixth, add 63 to both sides. / Your problem should look like: 27 + 63 = 5b
Seventh, simplify 27 + 63 to 90. / Your problem should look like: 90 = 5b
Eighth, divide both sides by 5. / Your problem should look like:
Ninth, simplify
Tenth, switch sides. Your problem should look like: b = 18
Answer: b = 18