Answer
The sequence is geometric.
$a_{n}=36\cdot \left(\frac{1}{3}\right)^{n-1}$
Work Step by Step
$\dfrac{12}{36}=\dfrac{4}{12}=\dfrac{\frac{4}{3}}{4}=\dfrac{\frac{4}{9}}{\frac{4}{3}}=\dfrac{\frac{4}{27}}{\frac{4}{9}}=\frac{1}{3}$
As $\frac{a_{n+1}}{a_{n}}=\frac{1}{3}$, that is, the ratio between each term and the preceding term is the same, the sequence is geometric.
Common ratio: $r=\frac{1}{3}$.
First term: $a_{1}=36$.
The general term is
$a_{n}=a_{1}\cdot r^{n-1}=36\left(\frac{1}{3}\right)^{n-1}$
