Answer:
C. 
Step-by-step explanation:
Given the two equations:

To find:
The correct option when value of y is substituted to 2nd equation using the 1st equation.
Solution:
First of all, let us learn about the substitution method.
Substitution method is the method to provide solutions to two variables when we have two equations and two variables.
In substitution method, we find the value of one variable in terms of the other variable and put this value in the other equation.
Now, the other equation becomes only single variable and then we solve for the variable's value.
Here, we have two equations and value of one varible is:

Let us put value of y in 2nd equation:

So, the correct answer is option C. 
Answer:
By plotting in the number in the equation (aka where all the x’s are variables are) and seeing if it works.
Step-by-step explanation:
For example, let’s use the problem:
3x + 4 = 16
if the given number is 4, we fill it in for x-
3 (4) + 4= 16
solve to see if true:
12 + 4 = 16
16 = 16
hence, the given number 4 makes the equation true!
hopes this helps, have a great day :)
Answer:
a is the _amplitude_(Length of the blades)_
The vertical shift, k, is the _Mill shaft height_


Step-by-step explanation:
In this problem the amplitude of the sinusoidal function is given by the length of the blades.

The mill is 40 feet above the ground, therefore the function must be displaced 40 units up on the y axis. So:

We know that the blades have an angular velocity w = 3 rotations per minute.
One rotation = 
1 minute = 60 sec.
So:


Finally:
a is the _amplitude_(Length of the blades)_
The vertical shift, k, is the _Mill shaft height_


Answer:
D
Step-by-step explanation:
You have to rearange the equation, so:
-4x+y=-4
y=4x-4
Following the formula for a line of y=mx+c.