Answer:
a9 = 26
Step-by-step explanation:
nth term of an arithmetic sequence an = a + (n-1)d
a16 = a+15d = 12.... 1
a7 = a+6d = 30.....2
Subtract
15d - 6d = 12 - 30
9d = -18
d =-18/9
d = -2
Substitute d = -2 into 1
a + 15d = 12
a+15(-2) = 12
a - 30 = 12
a = 12 + 30
a = 42
Get a9;
a9 = a+8d
a9 = 42+8(-2)
a9 = 42 - 16
a9 = 26
hence the 9th term of the sequence is 26
