Give the step-by-step reasoning process and then the final answer. Dennis collected 10 rocks. He put all of them in his aquarium but his fish ate half of them. He was able to make the fish spit two out. How many of Dennis's rocks are left?
Dennis had 10 / 2 = 5 rocks left after the fish ate them. He made the fish spit two out, which left Dennis with 5 + 2 = 7 rocks.
The final answer: 7.