Answer:
The dog will reach the tree first.
Step-by-step explanation:
If the tree is 30 yards from the dog's starting position, and the cat is 10 yards ahead of the dog, then the cat is 20 yards away from the tree. The dog runs at 8 yps, and the cat runs at 6yps. The cat would get there in approximately 3 seconds, and the dog would be ahead of the cat by 3 yards within 2 seconds, so the dog would be there before the cat would.