Answer:
Value of x is used to consider unknown value. The letter “x” is commonly used in algebra to indicate an unknown value. It is referred to as a “variable” or, in some cases, a “unknown.” In x + 2 = 7, x is a variable. ... A variable need not be “x,” but might be “y,” "w," or any other letter, name, or symbol.
Answer:

Step-by-step explanation:
Assuming this complete problem: "A cell tower is located at (-8, 4) and transmits a circular signal that covers three major cities. The three cities are located on the circle and have the following coordinates: G (-4, 7), H (-13, 4), and I (-8, -1). Find the equation of the circle"
For this case the generla equation for the circle is given by:

From the info we know that the tower is located at (-8, 4) so then h = -8 and k = 4, so then we need to find the radius. So we have the equation like this:
If the 3 points are on the circle then satisfy the equation. We can use the first point (-4,7) and if we replace we can find the value for 

So then 
And if we replace the second point we got this:

And for the third point we have:

And we got the same result.
So then our final equation is given:

Answer:
12.5 un^2
Step-by-step explanation:
The formula for area of a trapezoid is (a+b)/2 *h
a and b are the shorter and longer bases respectively. H is height, you have both.
Simply plug it into the equation and find your answer.
(2.5+7.5)/2 *2.5 = 5*2.5 which is equal to 12.5. Add units.
Answer:

Step-by-step explanation:
If the population increases at a rate of 4% per annum, then:
In year 1:

Where
is the initial population and
is the population in year n
In year 2

It can also be written as:

Taking out common factor

Taking out common factor (1 + 0.04)

Taking out again common factor 
Simplifying

So

This is the equation that represents the population for year n
Then, in 4 years, the population will be:

THIS IS THE COMPLETE QUESTION BELOW;
The weekly salaries of sociologists in the United States are normally distributed and have a known population standard deviation of 425 dollars and an unknown population mean. A random sample of 22 sociologists is taken and gives a sample mean of 1520 dollars.
Find the margin of error for the confidence interval for the population mean with a 98% confidence level.
z0.10 z0.05 z0.025 z0.01 z0.005
1.282 1.645 1.960 2.326 2.576
You may use a calculator or the common z values above. Round the final answer to two decimal places.
Answer
Margin error =210.8
Given:
standard deviation of 425
sample mean x=1520 dollars.
random sample n= 22
From the question We need to to calculate the margin of error for the confidence interval for the population mean .
CHECK THE ATTACHMENT FOR DETAILED EXPLANATION