13806 : 531 = 26

 
30240 : 420 = 72

 
7009 * 24 = 168216
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}7009\\ 24\end{array}}\\ 28036\\ 14018\phantom{0}\\ \overline{168216}\end{array}$
 
5060 * 73 = 369380
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}506\\ 73\end{array}}\\ 1518\\ 3542\phantom{0}\\ \overline{36938}\end{array}$
 
1000 − 100 : 5 * (2 + 8) = 1000 − 100 : 5 * 10 = 1000 − 20 * 10 = 1000 − 200 = 800
 
1000 − (100 : 5 * 2 + 8) = 1000 − (20 * 2 + 8) = 1000 − (40 + 8) = 1000 − 48 = 952