Okay, here we have this:
Considering the provided equation of the line n(x), the form of the equation y = mx + b, where m represents the slope, that in a line if the slope is positive the line is increasing, and if it is negative the line is decreasing, so we obtain the following:
For the case of the line n the slope is equal to -1/3, this means that the slope is negative, therefore the line is decreasing.