It seems it should be the other way... . How soon will the puppy catch up with the kitten.
The way you have it the kitten will never catch the pup. There is already 180m between them so, the distance will only increase because the puppy runs faster than the cat.
If the puppy runs after the cat, will eventually catch up with it and can be calculated. Not the other way around.
If the pup runs after the cat, the distance between them will decrease and the pup will catch the cat.
