What I did was 27.99-21.59 which equals 6.40 and then times that by 12 which brings you to 76.80
To compute the mean, you simply have to sum all the elments in the data set and the divide the sum by the number of elements:

To compute the variance, we first need to compute the distance of each element from the mean. To do so, we build a "parallel" dataset, given by the difference of every value and the mean:


Now we need those difference squared:

The variance is the mean of this new vector, so

Finally, the standard deviation is simply the square root of the variance, so you have

12
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Answer:
Step-by-step explanation:
A) 5x - 7 = 5x becomes -7 = 0 if 5x is subtracted from both sides. This result is never true, so NO SOLUTION
B)3x−9=3(x−3) Performing the indicated multiplication, we get
3x - 9 = 3x - 9. This is always true, so there are INFINITELY MANY SOLUTIONS
C)2x−6=−2(x−3) Performing the indicated multiplication, we get
2x - 6 = -2x + 6. Adding 2x - 6 to both sides results in
4x - 12 = 0, or 4x = 12. Thus, the solution is x = 3. ONE SOLUTION
D)2x+6−5x=−3(x This equation is incomplete