The equation of the given line, y = 3x - 2, is written in slope-intercept form:
... y = mx + b
where m represents the slope and b is the y-intercept.
Matching the form to the given equation, you see m = 3, and b = -2. The slope of the given line is 3.
The slope of a line perpendicular to it will be the negative reciprocal of this value
... slope of perpendicular line = -1/m = -1/3
For some new value of b, the equation of the perpendicular line can be written
... y = (-1/3)x + b
Filling in the values of the point coordinates, we can find the appropriate value of b.
... 4 = (-1/3)(3) +b
... 4 = -1 + b . . . . . . . simplify
... 5 = b . . . . . . . . . . add 1
Then the equation you want is ...
... y = (-1/3)x + 5