y=0.25x-7
y=1/4x-7
Slope of this line has a value of 1/4.
We know that k1*k2=-1 (if lines are perpendicular)
Then k2=-4
The equation of the second line is
y=-4x+b
If this line passes through the poin (-6;8), then 8=-4*(-6)+b
8=24+b
b=8-24
b=-16
The equation is y=-4x-16