Answer
$y = \frac{1}{2}x + \frac{5}{2}$
Work Step by Step
First compute the slope of the line with $(x_1, y_1) = (1, 3)$ and $(x_2, y_2) = (-1, 2)$.
Slope:
$m = \dfrac{y_2-y_1}{x_2-x_1}\\
m=\dfrac{2-3}{-1-1}\\
m=\dfrac{-1}{-2}\\
m=\dfrac{1}{2}$
Use the point $(1, 3)$ and the slope $\frac{1}{2}$ to get the point-slope form of the equation of the line, then isolate $y$ to obtain the slope-intercept form:
$y - 3 = \frac{1}{2}(x - 1)\\
y - 3 + 3 = \frac{1}{2}(x - 1) + 3\\
y = \frac{1}{2}x - \frac{1}{2} + 3\\
y = \frac{1}{2}x + 3 - \frac{1}{2}\\
y = \frac{1}{2}x + \frac{5}{2}$
