Solution:
The slope is expressed as
[tex]\begin{gathered} m=\frac{y_2-y_1}{x_2-x_1} \\ where \\ (x_1,y_1)\text{ and} \\ (x_2,y_2)\text{ are the coordinates of points through which the line passes} \end{gathered}[/tex]Given that the points (-5, -5) and (r, 1) lie on the line with slope 1/2, this implies that
[tex]\begin{gathered} x_1=-5 \\ y_1=-5 \\ x_2=r \\ y_2=1 \end{gathered}[/tex]By substituting these valus into the slope formula, we have
[tex]\begin{gathered} \frac{1}{2}=\frac{1-(-5)}{r-(-5)} \\ \Rightarrow\frac{1}{2}=\frac{1+5}{r+5} \\ cross-multiply, \\ r+5=2(1+5) \\ \Rightarrow r+5=12 \\ add\text{ -5 to both sides of the equation,} \\ r+5-5=12-5 \\ \Rightarrow r=7 \end{gathered}[/tex]Hence, the missing coordinate r is evaluated to be
[tex]7[/tex]