First, convert 1 2/5 miles to decimal form. That's 1.4 miles. Then convert 5/8 to decimal. That's .625. So, we know that 1.4 miles is .625 of the distance (x) around the park. Here's the equation, and the solution is just division. Easy!
1.4 miles = .625x
1.4/.625 = 2.24 miles