Answer:
Part A) see the explanation
Part B) 
Step-by-step explanation:
Part A)
we know that
A relationship between two variables, x, and C, represent a proportional variation if it can be expressed in the form
or 
Let
C ---> is the total cost (represent the output or dependent variable)
x ----> is the number of books (represent the input or independent variable)
In this problem
we have a proportional relationship between the variables x and C
Part B) we know that
The linear equation is given by

The constant of proportionality k is the same that the slope or unit rate of the linear equation
In this problem the constant k is given

so

For x=12 books
substitute in the equation and solve for C

In function notation

Answer:
1) the third equation or X/2=2.0
2) 20 bucks
Step-by-step explanation:
for number 1 just plug in the x hi 4 and try to solve it
2) just calculate unit rate by 120/6=20
Yes it is a polynomial .
The degree of polynomial is 4 and there is no power as a fraction or negative integer
Answer:
105.26
Step-by-step explanation: