Variance of a continuous random variable X is defined as
Standard deviation is defined as

Hence standard deviation is the positive square root of variance.
9x + 1 = 7x - 9
-7x. -7x
2x + 1 = -9
-1. -1
2x = -10
Divide by 2
x = -5
2(x - 2) = -4x + 44
First, expand. / Your problem should look like:
Second, add 4 to both sides. / Your problem should look like:
Third, simplify -4x + 44 + 4 to get -4x + 48. / Your problem should look like:
Fourth, add 4x to both sides. / Your problem should look like:
Fifth, add 2x + 4x to get 6x. / Your problem should look like:
Sixth, divide both sides by 6. / Your problem should look like:
Seventh, simplify

to 8. / Your problem should look like:

Answer:
x = 8
Q1
the clothes are on 45% discount, wich mean they become 55% of their original price.
30× 55% =16.5
64×55%=35.2
the new salary is 103% of the original
10×103% = 10.3
11600×103% = 11,948
Q2:
1+0.24= 1.24
1- 0.27= 0.73
86×140%= 120.4
440×119%= 523.6
82×90% = 73.8
480× 73%= 350.4
A. 7/11= 7 ÷ 11
B. 5/2= 5 ÷ 2
C. 9/10= 9 ÷ 10
D. 7/15= 7 ÷ 15
A fraction is just a division problem. 7/11 would be considered 7 ÷ 11 (or just 7/11) just do the same for the rest of the fractions.