[tex]\bf n^{th}\textit{ term of an arithmetic sequence}
\\\\
a_n=a_1+(n-1)d\qquad
\begin{cases}
n=n^{th}\ term\\
a_1=\textit{first term's value}\\
d=\textit{common difference}\\
----------\\
a_1=-2\\
d=5\\
n=9
\end{cases}
\\\\\\
a_9=-2+(9-1)5\implies a_9=-2+40[/tex]