Help 6 ​

6. Not arithmetic because the difference between terms is not constant

7.  12th term  =

15  - 4 (12 - 1)  =

15 - 4(11)  =

15  -  44 =

-29

8.  To find the missing term

[ First term + Third term ]  /  2   =

[ 20 + 32 ]  / 2

52  / 2  =

26