Given data:
The given equation of line is y=x/4+5.
The given y-intercept is (0,c)=(0,-3).
The standard equation of line is,
y=mx+c
Compare the given equation with the above expression.
m=1/4
The expression for the slope which is perpendicular to the given line.

The equation of the line which is perpendicular to the given line is,

Thus, the line which is perpendicular to the given line is y=-4x-3.