Answer
$y=5$, or, in general form, $y-5=0$
Work Step by Step
Through $(4,5);$ parallel to the $x$-axis
A point through which the line passes is given. The fact that the line is parallel to the $x$-axis is also known.
If the line is parallel to the $x$-axis, then it's completely horizontal and its equation can be represented just by making $y$ equal to the $y$ coordinate of some point through which the line passes.
The equation of this line is:
$y=5$, or, in general form, $y-5=0$
