ANSWER
5 miles
Step-by-step explanation
Let's draw the two possible paths Bob can take. One is walking 3 miles south and 4 miles west, and the other is walking in a straight line from where he is to the park,
If Bob takes the red path, the total distance he will travel is 7 miles. If he takes the blue path, the total distance he will travel can be found with the Pythagorean Theorem,
Solve for c taking the square root of both sides,
Replace a and b, and solve,
Hence, the distance Bob will walk if he takes the blue path is 5 miles, which is the shortest path.