Our line is
x - 3y + 16 = 0.
We solve for y and find:
y = 1/3x + 16/3.
The slope of the line is 1/3.
The slopes of perpendicular lines are negative reciprocals. Let m is the unknown slope.
m (1/3) = -1.
m = -3.
We can use the point slope formula to find the equation:
y - yo = m(x - x0).
In our case, x0=5 and yo=1, and the slope is m=-3.
The equation:
y - 1 = -3(x - 5).