[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=-7\\
d=0.5\\
n=8
\end{cases}
\\\\\\
a_8=a_1+(8-1)d\implies a_8=-7+(8-1)(0.5)[/tex]
and surely you know how much that is.
