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?
How many rocks did the fish eat? ** Dennis had 10/2=<<10/2=5>>5 rocks left after the fish ate them.
How many rocks did the fish spit out? ** He made the fish spit two out, which left Dennis with 5+2=<<5+2=7>>7 rocks.
#### 7