Lets begin by finding the slope of line m, lets call the slope s, to find it we use those two points of the line m and calculate the x and y segments:
s = (-6 - 3)/(-2 + 5) = -9/3
s = -3
therefore the slope of lines m and n is -3, now we do have all what is needed to write the n line equation, we have the slope = -3 and the y-intercept of -2/3, the line equation with these data is like this:
y = mx + b, where m is the slope and b the y-intercept, so we substitute:
y = -3x -2/3
that is the n line equation