To get from home to her friend Stefan's house, Whitney would have to walk 4 miles due north. To get from home to her friend Katie's house, Whitney would have to walk 3 miles due east. What is the straight-line distance between Stefan's house and Katie's house? miles

Step 1 ：\text{Let } S \text{ be Stefan's house, } K \text{ be Katie's house, and } H \text{ be Whitney's home.}

Step 2 ：\text{By the Pythagorean theorem, } SK^2 = SH^2 + HK^2.

Step 3 ：\text{Substitute the given values: } SK^2 = (4)^2 + (3)^2.

Step 4 ：SK = \sqrt{16 + 9}.

Step 5 ：SK = \sqrt{25}.

Step 6 ：SK = 5