I'll show you how to do one of the equations and one of the inequalities. All the others are done exactly in the same way: you'll only have to change the numbers, and it will be a good exercise.
Equations
Let's take the first equality as an example: we have

By definition, the absolute value of a number is the positive version of that number: if the number is already positive the absolute value doesn't change it; if a number is negative the absolute value changes its sign.
So, if the absolute value of a number is 5, than that number was already 5, or it was -5, and the absolute value changed it to positive 5.
So, the solutions are given by

Inequalities
Again, we'll use the first one as example. We have

By the same logic as before, the absolute value of a number is greater than 7 if the number is already greater than 7, or if it is smaller than -7. For example, we have |-10|=10>7.
So, we have

Instead, if we have an inequality with the "less than" sign, we have for example

Answer:
The length of the arc is 8*pi cm. An arc that subtends a central angle of 120 degrees has a length of 120/360 = 1/3 the length of the total circumference of the circle. We know the entire circumference of the circle is 2πr, which in this case is 2π*12 = 24π.
Step-by-step explanation:
sorry I only have the 8
<span>B. The sample might not be representative of the population because it only includes students who are attending an after-school activity.</span>
I converted everything into decimals and went from there.
For sake of convenience, reverse the series, then it would be:
21,19,17.....7
a=21, d = -2,
s(4) = 4/2 (21+15)
s(4)=2(36)
s(4) = 72