Depends on where you are in the math book but this would be the most simple way.
n= number
sqar(-1) = i
For this case we have by definition, that the equation of a line in the slope-intersection form is given by:

Where:
m: It is the slope of the line
b: It is the cut point with the "y" axis
We have, according to the data provided, that the line is of the form:

That means that the slope is -1.
ANswer:

The answer is A. because the first part shows the ratio 3:2 and the other 2 shows equivalent ratios.