Sharon and her camping group hiked 6 miles due north, stopped for lunch, and then hiked 8 miles due west, stopping at ther campsite for the night. What is the straight line distance from their original starting place to the campsite?

Because you're looking for the hypotenuse of a right triangle, use the Pythagorean Theorem:

a^2 + b^2 = c^2
6^2 + 8^2 = c^2
36 + 64 = c^2
100 = c^2
10 = c