9m - (4m - (3m - (12m + 12)))
= 9m - (4m - (3m - 12m - 12))
= 9m - (4m - (-9m - 12))
= 9m - 4m + 9m + 12
= 14m + 12

6z - (13z - ((q - 13z) - 7q))
= 6z - (13z - (q - 13z - 7q))
= 6z - (13z - q + 13z + 7q)
= 6z - 13z + q - 13z - 7q
= -20z + q - 7q
= -20z - 6q