Answer
Geometric with a common ratio of $1.5$.
Work Step by Step
Check if there is a common ratio by diving two consecutive terms:
$\dfrac{15}{10}$ $=1.5$;
$\dfrac{22.5}{15}$ $=1.5$ ;
$\dfrac{33.75}{22.5}$ $=1.5$.
The ratio is constant so this is geometric.The common ratio is $1.5$
