I don't see how to get around using spacing, but I would do something like:

\(\displaystyle \begin{array}{cc} & 12 \\ + & 13 \\ \hline & 25 \end{array}\)

\(\displaystyle \begin{array}{cc} & 12 \\ \times & 13 \\ \hline & 36 \\ & 12\quad \\ \hline &156\,\,\,\, \end{array}\)