Answer:
80 is the constant of the variation.
\begin{gathered} \\ \tt{}y = \frac{k}{x} \end{gathered}
y=
x
k=
\begin{gathered} \\ \tt{}8 = \frac{k}{10} \end{gathered}
8=
10
k
\begin{gathered} \\ \tt{}8 \times 10 = k\end{gathered}
8×10=k
\begin{gathered} \\ \tt{}80 = k\end{gathered}
80=k
\begin{gathered} \\ \boxed{ \large \boxed{ \tt{}k = 80}} \\ \\ \\ \end{gathered}
k=80
