Answer:
r = 2
Step-by-step explanation:
Slope formula: [tex]m=\frac{y_2-y_1}{x_2-x_1}\\[/tex]
Substitute the known values for their respective variables and solve for the missing coordinate, r.
[tex]m=\frac{y_2-y_1}{x_2-x_1}\\\\ -\frac{1}{2}=\frac{6-r}{-12-(-4)}\\\\-\frac{1}{2}=\frac{6-r}{-8}\\\\ -8(-\frac{1}{2})=(\frac{6-r}{-8})-8\\\\ 4=6-r\\\\4-6=6-r-6\\\\-2=-r\\\\\frac{-2}{-1}=\frac{-r}{-1}\\\\ 2=r[/tex]