Chapter 9 - Sequences and Series - 9-2 Arithmetic Sequences - Practice and Problem-Solving Exercises - Page 575: 31

The $17^{\text{th}}$ term is $2$.

The $18^{\text{th}}$ term is $-9$ and the common difference is $-11$ so we simply subtract $-11$ from $-9$ to get the $17^{\text{th}}$ term: $a_{17}=a_{18}-d$ $a_{17}=-9-(-11)$ $a_{17}=-9+11$ $a_{17}=2$