Row 1, column 1:
Hint: Row 1 of $A$ is $\begin{pmatrix} -8 & 0 \end{pmatrix}$. Column 1 of $\mathbf{v}$ is $\begin{pmatrix} 1 \\ 8 \end{pmatrix}$. Multiply in pairs and add the results.
Row 2, column 1:
Hint: Row 2 of $A$ is $\begin{pmatrix} -4 & 8 \end{pmatrix}$. Column 1 of $\mathbf{v}$ is $\begin{pmatrix} 1 \\ 8 \end{pmatrix}$. Multiply in pairs and add the results.