Find the 10th term of the following sequences: a) 8, 3, -2, -7, ... b) 3, 1, 1/3, 1/9, ...

Calculate the difference between consecutive terms:
$3 - 8 = -5$
$-2 - 3 = -5$
$-7 - (-2) = -5$
Since there is a common difference, $d = -5$, this is an arithmetic sequence. The first term is $a_1 = 8$.

The formula is $a_n = a_1 + (n-1)d$. We need to find the 10th term, so $n=10$.

The 10th term is $\boxed{-37}$.

Calculate the ratio between consecutive terms:
$\frac{1}{3}$
$\frac{1/3}{1} = \frac{1}{3}$
$\frac{1/9}{1/3} = \frac{1}{9} \times 3 = \frac{3}{9} = \frac{1}{3}$
Since there is a common ratio, $r = \frac{1}{3}$, this is a geometric sequence. The first term is $a_1 = 3$.

The formula is $a_n = a_1 r^{n-1}$. We need to find the 10th term, so $n=10$.

The 10th term is $\boxed{\frac{1}{6561}}$.