(9a + 7b - 6c) - (2a - 3b + 4c) is equal to:

1. 7x + 7b + 10c

2. 7a + 10b - 10c

3. 7a - 10b + 10c

4. 7a - 10b - 10c

-81a⁵b⁴c³ ÷ (-9a²b²c) is equal to:

1. -9a³b²c²

2. 3a³b²c²

3. 9a⁴b

4. 9a³b²c²