First, solve for slope.
Formula for slope: [tex] \frac{y2-y1}{x2-x1} [/tex]
Plug in values: [tex] \frac{1-3}{5-1}= -\frac{2}{4} = -\frac{1}{2} [/tex]
Slope: [tex]- \frac{1}{2} [/tex]
Second, we must plug into point-slope form.
Formula for point-slope: [tex]y - y1 = m(x-x1) [/tex]
Plug in the values: [tex]y - 3 = - \frac{1}{2}(x-1)[/tex]
And there you have your answer in point-slope form.