387 : x = 513 : 57
387 : x = 9
x = 387 : 9
x = 43
Вычисления:

$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}387\\ \phantom{0}\underset{¯}{36}\\ \phantom{0}\underset{¯}{\phantom{0}}27\\ \phantom{00}\underset{¯}{27}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)9}\\ \overline{\overline{)43}}\end{array}\end{array}$
 
y : 6 = 54 * 8
y : 6 = 432
y = 432 * 6
y = 2592
Вычисления:
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}54\\ 8\end{array}}\\ 432\end{array}$
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}432\\ 6\end{array}}\\ 2592\end{array}$
 
3210 − x = 665 : 7
3210 − x = 95
x = 3210 − 95
x = 3115
Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}665\\ \phantom{0}\underset{¯}{63}\\ \phantom{0}\underset{¯}{\phantom{0}}35\\ \phantom{00}\underset{¯}{35}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)7}\\ \overline{\overline{)95}}\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}3210\\ 95\end{array}}\\ \begin{array}{r}3115\end{array}\end{array}$