Perpendicular lines have slopes whose product is -1.
If the original line has slope 3, the line that is perpendicular has slope -(1/3) Now use the point slope form of the line.
y - y1 = m(x - x1)
If (x1,y1) = (2,2) - your point, then:
y - 2 = (-1/3)(x - 2)
you can convert this into slope-intercept form.
y - 2 = (-1/3)x + (2/3)
y = (-1/3)x +(8/3)
Both equations represent the same line.