13a
12a- 6a + a = 7a Since they all have the same variable, you can simply add and subtract 12-6 = 6 6+1 = 7
It is: 12a+2 when simplified
-24
First you find like terms so you subtract 12-9 Then you get 3a Your other like terms are 3+18 Then you get 21 So your answer is 3a+21
13a
12a- 6a + a = 7a Since they all have the same variable, you can simply add and subtract 12-6 = 6 6+1 = 7
21a - 6a
12a + 6b + 9a + 14b =(12a + 9a) + (6b + 14b) =21a + 20b
It is: 12a+2 when simplified
-24
12a + a - 3a = 10a
12*a+8 =12a+8
First you find like terms so you subtract 12-9 Then you get 3a Your other like terms are 3+18 Then you get 21 So your answer is 3a+21
18
It multiplies out as: 12a-12+2 = 12a-10
That depends what the value of a is.