a. The first variable is x and the second variable is y.
b. The equations are 
and 
Step-by-step explanation:
Step 1:
The first step is to define the variables. The variables can be any two symbols, letters, characters, etc.
Here let the first variable be x and the let the second variable be y.
So the variables are defined as x and y.
Step 2:
The sum of the given variables is 12.
The first variable + the second variable = 12,
The difference between the two variables is 4.
The first variable - the second variable = 4.
Step 3:
If we add both the equations we get, 
and 
x = 8 and y = 4.
2. y=2x+3
When x =0 and y= something, the 'something' is your y-intercept which is b in the y=mx+b formula. Then we look at what is changed in the x and y value to determine the m part. the x increase by 1 and y increase by 2 so the m part is 2.
3. y=-7x
Same as the last one, there is no y-inter this time because the y=0 when x=0/ So the y deceased by 7 each time and x incease by 1 so it is -7 for the m part.
The volume of a cone with a diameter of 30 feet and a height of 60 feet is 14130.
<h3>What is the volume of a cone?</h3>
The volume of the cone is given by;
The volume of a cone with a diameter of 30 feet and a height of 60 feet.
The radius of the cone is;
Substitute all the values in the formula
Hence, the volume of a cone with a diameter of 30 feet and height of 60 feet is 14130.
Learn more about the volume of cone here;
brainly.com/question/3013784
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Answer: perceived lack of anonymity
Step-by-step explanation:
The source of bias that occurs when a group of students are asked to evaluate their teacher mid-quarter is a perceived lack of anonymity.
Perceived lack of anonymity occurs when the responder is afraid that if he or she gives an honest answer, it can end up affecting them negatively.
In this case, the students may be afraid that giving an honest opinion on the teacher will affect them.
