20782 + 5203 + 63870 = 25985 + 63870 = 89855
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}20782\\ 5203\end{array}}\\ \begin{array}{r}25985\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}25985\\ 63870\end{array}}\\ \begin{array}{r}89855\end{array}\end{array}$
 
4508 + 498 : 6 − 892 = 4508 + 83 − 892 = 4591 − 892 = 3699
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}498\\ \phantom{0}\underset{¯}{48}\\ \phantom{0}\underset{¯}{\phantom{0}}18\\ \phantom{00}\underset{¯}{18}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)6}\\ \overline{\overline{)83}}\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}4508\\ 83\end{array}}\\ \begin{array}{r}4591\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}4591\\ 892\end{array}}\\ \begin{array}{r}3699\end{array}\end{array}$