Answer:
82 miles
Step-by-step explanation:
When they stop, Harry is 18 miles north and Selma is 80 miles east
Their positions form the vertices of a right triangle with legs 18 and 80
Their distance from each other will be the hypotenuse of this triangle given by the Pythagorean theorem
[tex]c = \sqrt{a^{2} + b^{2}}[/tex]
where c is the hypotenuse and a, b the shorter legs
Given a = 18, b = 80
[tex]c = \sqrt{18^{2} + 80^{2}}\\\\c = \sqrt{324 + 6400}\\\\c = \sqrt{6724}\\\\\\c=82\\\\[/tex]
