We know that 3r-6=3(r-2) because 3*r is the same as 3r and we know that 3*-2 is -6 hence making them equal. And to check it we know that 3r-6 is equal to 3r-6.
x = -2 represents a vertical line that intersects the x axis at the point (-2, 0). Since the line is vertical, the slope is undefined making it not have a positive slope.
