the slope of the given line is 2/3. The slope of a line perpendicular to this given line is the negative reciprocal of 2/3, or -3/2.
The line passes thru (6,4). We can immediately write the desired equation as follows:
y - 4 = (-3/2)(x-6). This could, of course, be written differently:
y = 4 - (3/2)x + 9, or y = (-3/2)x + 9 (in slope-intercept form).