Answer:
![Rate\ of\ change=20](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ueaq8pn3oj7t552mxdr9t7fmfb19tiuq7h.png)
Explanation:
The Slope-Intercept form of an equation of a line is the following:
![y=mx+b](https://img.qammunity.org/2021/formulas/mathematics/middle-school/yj5waqmoy4i54laybzhhshd88hyo5w5rj5.png)
Where "m" is the slope of the line and "b" is the y-intercept.
By definition, the slope is:
![m=(change\ in\ y)/(change\ in\ x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/xm4hloar43i3doec1omyzorw0y7p0avva2.png)
Since the rate of change shows how a quantity changes in relation to another quantity, this is:
![Rate\ of\ change=m=(change\ in\ y)/(change\ in\ x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/jowcn34va1e7rlugoakyqepm7afsdrir55.png)
You must remember that It is a constant.
According to the information given in the exercise, a piece of the machinery loses $20 in value every month (Notice that this is constant) and its value after "m" months of service is $1,475.
Therefore, you can identify that:
![m=20](https://img.qammunity.org/2021/formulas/mathematics/middle-school/da9b6i38d67cniiz8tj9btkw9ulhwtpap1.png)
Then, you get that the rate of change in this situation is:
![Rate\ of\ change=m=20](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ei1m7k34wfs820x6id4er7mb5do3eh1vqe.png)