#### Answer

$a_{18}=-94$

#### Work Step by Step

In an arithmetic sequence, first we have to find the common difference, which can be calculated as the difference of any two subsequent terms:
$d=a_2-a_1=2-8=-6$
The n th term can be calculated as:
$a_n=a_1+d\times(n-1)$
The 18th term is:
$a_{18}=8+(-6)\times(18-1)=-94$