First, solve for slope.
Formula for slope: [tex] \frac{y2-y1}{x2-x1} [/tex]
Plug in values: [tex] \frac{8-5}{1-2} = -\frac{3}{1} = -3[/tex]
Slope: [tex]-3[/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 - 5 = -3(x - 2) [/tex]
And there you have your answer in point-slope form.