By definition, we have

So, we have to solve two different equations, depending of the possible range for the variable. We have to remember about these ranges when we decide to accept or discard the solutions:
Suppose that 
In this case, the absolute value doesn't do anything: the equation is

We are supposing
, so we can accept this solution.
Now, suppose that
. Now the sign of the expression is flipped by the absolute value, and the equation becomes

Again, the solution is coherent with the assumption, so we can accept this value as well.
The slope-intercept form:

The formula of a slope:

We have the points (-4, 47) and (2, -16). Substitute:

Therefore we have:

Put the coordinates of the point (2, -16) to the equation:

Answer: 
Answer:
domain = ( 3, 11, 121, 34, 23)
range = ( 21, 34, 1, 23)
She has to buy both binders and notebooks. So, you have to take into account that she has to have both. The closest you can get to $20 while still getting notebooks, is to buy 4 binders. 4 times 4 equals 16. So, she can get 4 binders and 2 notebooks, because then, 2 times 2 equals 4 and 16 plus 4 equals 20.
What?
The slope can be found between two points by finding the change in values divided by the change in values.