You can find this by first realizing that perpendicular lines have opposite and reciprocal slopes. So since it starts at 2/3 we flip it and make it a negative and the new slope is -3/2. Now we can use that and the point to get the y intercept using slope intercept form.
y = mx + b
5 = (-3/2)(-6) + b
5 = 9 + b
-4 = b
And now we can use our new slope and new intercept to model the equation.