Here is how I would set up this problem:
Logan: x
Samantha: 3x
Total: 45
Therefore we get the equation:
3x+x=45
Solve this equation for x:
3x+x=45
4x=45
x=11.25
Now refer back to how you set up the problem:
Logan: x
Samantha: 3x
Therefore, Logan's time was 11.25 minutes. To find Samantha's time, do 11.25(3)=33.75 because Samantha is 3 times as fast as Logan.
Logan's time: 11.25 minutes
Samantha's time: 33.75 minutes
To find the rates, you must have a unit of distance because: distance=rate(time)
rate=distance/time
Best of luck!