Distance formula:
[tex]d=\sqrt[]{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]where (x1,y1) and (x2, y2) are the points of interest.
Replacing whit (7,-1) and (3,8):
[tex]\begin{gathered} d\text{ = }\sqrt[]{(3-7)^2+(8-(-1))^2} \\ d=\sqrt[]{16+81} \\ d\text{ = }\sqrt[]{97} \end{gathered}[/tex]