When two lines are perpendicular, the product of their gradients is -@. Therefore the gradient of the line we need is -⅔. This is the x coefficient, so we have y=-⅔x+a where a is the y intercept.
Plug in the point (4,6): 6=-⅔×4+a, 6+8/3=a and a=26/3. So y=-⅔x+26/3=⅔(13-x).
Get rid of the fraction and we have 3y=2(13-x)=26-2x. In general form this is: 2x+3y-26=0.