# How do you write an equation of a line Perpendicular to y=3 passing through P(-2,4)?

$y = 3$ means a horizontal line (no $x$-influence).
So the perpendicular is a vertical line and thus of the form $x = a$
Since all $x$'s on this line are the same (including ${x}_{P}$), the line has the equation $x = - 2$