First, draw out a diagram of this so you understand it graphically.He goes 7 miles south, so you have a length that extends south that's 7 units long, then he goes east 3, then 3 north. The 3 north just brings his 7 miles back to 4. So in reality, he's only traveling 4 miles south, and 3 miles east. Seeing this makes a right triangle...plug in the values into the Pythagorean TheoremLa² + b² = c²3² + 4² = c²25 = c²c=5