tính 77 – 38

\(\begin{array}{l}\underline { - \begin{array}{*{20}{c}}{77}\\{38}\end{array}} \\\,\,\,\,39\end{array}\)

\(\begin{array}{l}\underline { + \begin{array}{*{20}{c}}{19}\\{65}\end{array}} \\\,\,\,\,84\end{array}\)

\(\begin{array}{l}\underline { - \begin{array}{*{20}{c}}{90}\\{\,\,\,8}\end{array}} \\\,\,\,\,82\end{array}\)

\(\begin{array}{l}\underline { + \begin{array}{*{20}{c}}{49}\\{19}\end{array}} \\\,\,\,\,68\end{array}\)