Distance formula:
[tex]d=\sqrt[]{(y_2-y_1)^2+(x_2-x_1)^2}[/tex]where (x1, y1) and (x2, y2) are the points of interest. Replacing with R(0, 1) and S(6, 3.5):
[tex]\begin{gathered} d=\sqrt[]{(3.5-1)^2+(6-0)^2} \\ d=\sqrt[]{2.5^2+6^2} \\ d=\sqrt[]{\frac{25}{4}+36} \\ d=\sqrt[]{\frac{25+36\cdot4}{4}} \\ d=\sqrt[]{\frac{169}{4}} \\ d=\frac{\sqrt[]{169}}{\sqrt[]{4}} \\ d=\frac{13}{2} \end{gathered}[/tex]