Answer
$y=2x+2$
Work Step by Step
Using $y-y_1=\dfrac{y_1-y_2}{x_1-x_2}(x-x_1)$ or the Two-Point Form, then the equation of the line passing through the given points, $(
3,8
)\text{ and }(
1,4
)$, is
\begin{array}{l}
y-8=\dfrac{8-4}{3-1}(x-3)
\\\\
y-8=\dfrac{4}{2}(x-3)
\\\\
y-8=2(x-3)
\\\\
y-8=2x-6
\\\\
y=2x-6+8
\\\\
y=2x+2
.\end{array}