Simplify each expression, then explain what property was used:
1. 6s + 2
Simplified expression:

Explanation:

2. s + 2s + 9 + s
Simplified expression:

Explanation:

3. 4(2s + r)
Simplified expression:

Explanation:

Combine Like Terms:
4. -3r - 3 + r + 7
5. 5s + 2s^ - 5s + 4s^

8. Use the model below to find the area:

9. Use the model below to find the side lengths: