Answer
$y=-x+6$
Work Step by Step
First, we find the slope as follows
$$
m=\frac{y_2-y_1}{x_2-x_1}=\frac{5-3}{1-3}=-\frac{2}{-2}=-1
.$$
The point-slope form of a line is given as:
$$y-y_1=m(x-x_1)$$
We plug in the given point and slope and solve for $y$:
$$y-3=- (x-3)\Longrightarrow y=- x+3+3=-x+6
.$$