The most important part of solving questions is going through the important information’s that are already given. Let us assume the total distance of their ride = x
 Then
 (3/5) * x = 15
 3x = 15 * 5
 3x = 75
 x = 75/3
 = 25 kilometers
 So the total distance for riding was 25 kilometers. I hope the procedure is clear enough for you to understand. Using this method you can always solve similar problems without requiring any help.