(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

(9a + 7b - 6c) - (2a - 3b + 4c)

= 9a + 7b - 6c - 2a + 3b - 4c

= (9a - 2a) + (7b + 3b) + (- 6c - 4c)

= 7a + 10b + (-10c)

= 7a + 10b -10c

Hence, option 2 is the correct option.