A polygon is a 2-dimension figure....
The equation of a line of the slope-intersection form is given by:

Where:
m: It's the slope
b: It is the cut-off point with the y axis
If two lines are parallel then their slopes are equal.
We have the following line:

Thus, the slope of the line is -5.
Therefore a parallel line is of the form:

We replace the point 

Finally, the equation is of the form:

Answer:

8 cm and 9 cm is the correct answer
Y= -1/2x - 4
hope this helps! :)
There ya go! The answer is 8 rows. Added a picture to show you my work :)