Here is the answer
I did it with steps
3a+2(4a-1)=9
3a+8a-2=9
11a=11
a=1
Answer:
6.18% of the class has an exam score of A- or higher.
Step-by-step explanation:
When the distribution is normal, we use the z-score formula.
In a set with mean
and standard deviation
, the zscore 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 pvalue, we get the probability that the value of the measure is greater than X.
In this question, we have that:

What percentage of the class has an exam score of A- or higher (defined as at least 90)?
This is 1 subtracted by the pvalue of Z when X = 90. So



has a pvalue of 0.9382
1 - 0.9382 = 0.0618
6.18% of the class has an exam score of A- or higher.
Practice proportionality. A 50 difference between 100 and 150 is less relevant than 50 in 25 and 75. Its like you have 1 billion dollars and i give you 10 dollars. Its worthless right? What if you have 20 dollars and i give you again 10 dollars, its half of what you have. See the difference? Same number but different value.
A. 10% is the answer
Step-by-step explanation: