Answer:
12r - 8 - 12
you have to combine like terms. below i have bolded the like terms:
12r - 8 - 12
together it combines to:
12r - 20
This question is solved applying the formula of the area of the rectangle, and finding it's width. To do this, we solve a quadratic equation, and we get that the cardboard has a width of 1.5 feet.
Area of a rectangle:
The area of rectangle of length l and width w is given by:

w(2w + 3) = 9
From this, we get that:

Solving a quadratic equation:
Given a second order polynomial expressed by the following equation:
.
This polynomial has roots
such that
, given by the following formulas:
In this question:


Thus a quadratic equation with 
Then


Width is a positive measure, thus, the width of the cardboard is of 1.5 feet.
Another similar problem can be found at brainly.com/question/16995958
14.6 is the constant because no matter how many hours she will work (that number could change) it will always be a linear growth of 14.6.