1. **State the problem:** We need to find the temperature at 11 pm given the temperature changes throughout the day starting from -7°C at midday. 2. **Understand the problem:** - Temperature starts at -7°C at 12 pm (midday). - It rises by 1°C per hour until 5 pm. - After 5 pm, it drops by 2°C per hour until 11 pm. 3. **Calculate the temperature rise from 12 pm to 5 pm:** - Number of hours from 12 pm to 5 pm is $5$ hours. - Temperature increase is $1 \times 5 = 5$°C. - Temperature at 5 pm is $-7 + 5 = -2$°C. 4. **Calculate the temperature drop from 5 pm to 11 pm:** - Number of hours from 5 pm to 11 pm is $6$ hours. - Temperature decrease is $2 \times 6 = 12$°C. - Temperature at 11 pm is $-2 - 12 = -14$°C. 5. **Final answer:** The temperature at 11 pm is **$-14$°C**.