1. **Simplify the expressions:** 1.) $5a + 6a = (5 + 6)a = 11a$ 2.) $3a + a = (3 + 1)a = 4a$ 3.) $8a - 3a = (8 - 3)a = 5a$ 4.) $10a - 2a = (10 - 2)a = 8a$ 5.) $9a + 4a = (9 + 4)a = 13a$ 6.) $11a - 7a = (11 - 7)a = 4a$ 7.) $4b + 3b = (4 + 3)b = 7b$ 8.) $12b - 6b = (12 - 6)b = 6b$ 9.) $5b + 9b = (5 + 9)b = 14b$ --- 2. **Complete the following expressions using order of operations (PEMDAS):** 1.) $12 \times 3 - 5 + 4 = 36 - 5 + 4 = 31 + 4 = 35$ 2.) $4 + 7 \times 2 - 8 = 4 + 14 - 8 = 18 - 8 = 10$ 3.) $5 - 7 + 2 \times 10 = 5 - 7 + 20 = -2 + 20 = 18$ 4.) $15 \div 3 + 8 \times 5 = 5 + 40 = 45$ 5.) $11 \times 3 - 12 \div 4 = 33 - 3 = 30$ 6.) $5 + 9 - 16 \div 2 = 5 + 9 - 8 = 14 - 8 = 6$ --- 3. **Combine like terms and simplify:** 1.) $3a(a + 4) - 2a + 7 = 3a^2 + 12a - 2a + 7 = 3a^2 + (12 - 2)a + 7 = 3a^2 + 10a + 7$ 2.) $5a + 3a - 15 \div 3 = 8a - 5 = 8a - 5$ 3.) $4(3 + 9) + 10a - 4a = 4 \times 12 + 6a = 48 + 6a$ 4.) $(21 \div 7)(4a + a) - 12 = 3 \times 5a - 12 = 15a - 12$ 5.) $17 + 4(3 + a) - a = 17 + 12 + 4a - a = 29 + 3a$ 6.) $10a - 4a + 27 \div 3 = 6a + 9$ **Final answers:** Simplify: 11a, 4a, 5a, 8a, 13a, 4a, 7b, 6b, 14b Complete: 35, 10, 18, 45, 30, 6 Combine: $3a^2 + 10a + 7$, $8a - 5$, $48 + 6a$, $15a - 12$, $29 + 3a$, $6a + 9$