x + 4y = 9 Convert to slope / intercept form:-
y = (-1/4)x + 9/4
so the line perpendicular to this will have a slope -1 /(-1/4) = 4
so our equation will be y - y1 = 4(x - x1) where x1y1 is a point on the line.
x1 = 8 and y1 = -3:-
y - -3 = 4(x - 8)
y = 4x - 35
-4x + y = -35 is the answer