Sure! Here are the negative and interrogative forms of the sentences you provided:

1. **Sentence:** They were in Rio last summer.
- **Negative:** They were not in Rio last summer.
- **Interrogative:** Were they in Rio last summer?

2. **Sentence:** We did our exercise this morning.
- **Negative:** We did not do our exercise this morning.
- **Interrogative:** Did we do our exercise this morning?

3. **Sentence:** My parents came to visit me last July.
- **Negative:** My parents did not come to visit me last July.
- **Interrogative:** Did my parents come to visit me last July?

4. **Sentence:** The hotel was very expensive.
- **Negative:** The hotel was not very expensive.
- **Interrogative:** Was the hotel very expensive?

5. **Sentence:** I had a bicycle when I was young.
- **Negative:** I did not have a bicycle when I was young.
- **Interrogative:** Did I have a bicycle when I was young?

6. **Sentence:** The children went to the zoo yesterday.
- **Negative:** The children did not go to the zoo yesterday.
- **Interrogative:** Did the children go to the zoo yesterday?

7. **Sentence:** Ernie ate the last doughnut.
- **Negative:** Ernie did not eat the last doughnut.
- **Interrogative:** Did Ernie eat the last doughnut?

8. **Sentence:** They bought a new house last month.
- **Negative:** They did not buy a new house last month.
- **Interrogative:** Did they buy a new house last month?

Feel free to reach out if you need further assistance!