It will prove convenient to express the dot product in a form where its left input is a row vector, and its right input is a column vector.

So we would write:

\$\begin{bmatrix} 1 & 2 \end{bmatrix} \cdot \begin{bmatrix} 10 \\\\ 20 \end{bmatrix} = 1 \cdot 10 + 2 \cdot 20 =50 \$