(5a - 4b) + (2c - 3b - 6c) + a =5a - 4b + 2c - 3b - 6c + a =(5a + a) + (-4b - 3b) + (2c - 6c) =[ 6a - 7b - 4c ].
-6(a-3b-9c)
6+7a+6b
6a+7b
11a+11b
-2a plus 3b
12a + 6b + 6c = 6(2a + b + c)
No
20a2b2
2a
-13
6a+7b. This cannot be simplified anymore unless you know a or b.