Question 387190
A line is perpendicular to another line if their slopes are related this way:
{{{m[1] = -1/m[2]}}}
where {{{m}}} means slope of the line(s)
It is given that a line has the equation {{{y = -3}}}
You usually find {{{m}}} by comparing the given equation
with the general equation {{{y = mx + b}}}, but what
you have is more like {{{y = b}}} where {{{b = -3}}},
so {{{m[2]}}} must be zero.
What is {{{m[1]}}}?
{{{m[1] = -1/0}}}
{{{m[1]}}} = infinity, or a vertical slope.
So, you have a vertical line that goes through (2,4).
All vertical lines have the form {{{x = k}}} 
From (2,4), I see that the line is {{{x = 2}}}