Answer:
(y - 7) = (-1/3)(x - 8)
Explanation:
slope of a line perpendicular to another line is the negative reciprocal of the other line's slope (other line's slope in this case is 3 so the slope of our line will be -1/3)
point slope form: (y - y1) = m (x - x1)
y1 in this case is 7
x1 in this case is 8
so....
(y - 7) = (-1/3)(x - 8)