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:
139968
Step-by-step explanation:
Multiply the all of the numbers together and you have your answer (:
Answer:
2d-3
Step-by-step explanation:
it may help you to understand
Answer:
a
Step-by-step explanation:
cause you go up 14 and over 6 then you divid by 2 and get 7/3