tính 78 + 15

\(\begin{array}{l}\underline { + \begin{array}{*{20}{c}}{78}\\{15}\end{array}} \\\,\,\,\,93\end{array}\)

\(\begin{array}{l}\underline { - \begin{array}{*{20}{c}}{42}\\{19}\end{array}} \\\,\,\,\,23\end{array}\)

\(\begin{array}{l}\underline { + \begin{array}{*{20}{c}}{81}\\{19}\end{array}} \\\,100\end{array}\)

\(\begin{array}{l}\underline { - \begin{array}{*{20}{c}}{57}\\{\,\,\,8}\end{array}} \\\,\,\,\,49\end{array}\)