Step-by-step explanation:

in 2nd exp. this is because by using the formula of a2-b2
Answer:
By knowing the standard deviation, one gets the idea of how the value is scattered or dispersed about the mean.
Step-by-step explanation:
Let us first define standard deviation.
As it is known that the standard deviation is a measure of dispersion which express the spread of observation in terms of the average of deviations of observations from some central values.
Measure of dispersion gives us an idea about homogeneity or heterogeneity of the distribution.
Standard deviation is supposed almost an ideal measure of dispersion except the general nature of extracting the square root.
Thus for the given question, if we want to compare the two different groups of students whose mean score is 85. Here the standard deviation for both the groups interprets an idea about how the individual score for each group scattered or varied about the mean score i.e. 85.
The best way to do this question is to use elimination. Elimination is a way to find out the POINT OF INTERSECTION between two lines. Let me show you how.
3y+4x=3
x+3y=-6
Elimination is a way to remove any same variable with the same coefficient. In this case, there is 3y in both equations. In this case, we subtract to eliminate.
3y-3y+4x-x=3+6 It's plus 6 because two negatives become positive.
3x=9 Divide both sides by 3
x=3
Now you can find y.
x+3y=-6
3+3y=-6
3y=-9
y=-3
Therefore, the POI is (3,-3). I hope you understand this. Make sure to mark as brainliest.
Using .25N, you set N equal to 18 for 18 quarters. so .25(18) = 4.50