Apply the distance formula:
[tex]D=\sqrt[]{(x2-x1)^2+(y2-y1)^2}[/tex]Where;
(x1,y1) = (5,6)
(x2,y2) = (7,8)
Replacing:
[tex]D=\sqrt[]{(7-5)^2+(8-6)^2}[/tex][tex]D=\sqrt[]{(2)^2+(2)^2}[/tex][tex]D=\sqrt[]{4+4}[/tex][tex]D=\sqrt[]{8}[/tex][tex]D=2.83[/tex]