We can put this into y= mx + b to find the slope (m)
So we have
2x - 3y = 8 subtract 2x from each side
-3y = -2x + 8 divide each side by -3
y = 2/3x - (8/3)
So the slope of this line = 2/3
And the slope of a line perpendicular to this will have a negative reciprocal slope = -3/2