Answer: 20 Miles
Step-by-step explanation:
19 miles north and then 3 miles south is just 16 miles north.
16 miles west and then 4 miles east is just 12 miles west.
√16^2+12^2 = √256 + 144
√256+144 = √400
√400 = 20
The traveler is 20 miles from the original starting point.
(I honestly don't know why you'd use this formula, but it's what I was taught.)