As it's moving in North and east, forming a 90°,
The displacement will be along the hypotenuse
Displacement:
[tex] = \sqrt{{80}^{2} + {60}^{2} }[/tex]
[tex] = \sqrt{6400 + 3600} [/tex]
[tex] = \sqrt{10000} [/tex]
[tex] = 100 \: miles[/tex]
The displacement is 100 miles