16x = 240
x = 240 : 16
x = 15
Ответ: x = 15

Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}240\\ \phantom{0}\underset{¯}{16}\\ \phantom{0}\underset{¯}{\phantom{0}}80\\ \phantom{00}\underset{¯}{80}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)16}\\ \overline{\overline{)15}}\end{array}\end{array}$

x * 12 = 312
x = 312 : 12
x = 26
Ответ: x = 26

Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}312\\ \phantom{0}\underset{¯}{24}\\ \phantom{0}\underset{¯}{\phantom{0}}72\\ \phantom{00}\underset{¯}{72}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)12}\\ \overline{\overline{)26}}\end{array}\end{array}$

x : 23 = 31
x = 31 * 23
x = 713
Ответ: x = 713

Вычисления:
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}31\\ 23\end{array}}\\ 93\\ 62\phantom{0}\\ \overline{713}\end{array}$

448 : x = 14
x = 448 : 14
x = 32
Ответ: x = 32

Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}448\\ \phantom{0}\underset{¯}{42}\\ \phantom{0}\underset{¯}{\phantom{0}}28\\ \phantom{00}\underset{¯}{28}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)14}\\ \overline{\overline{)32}}\end{array}\end{array}$

5x + 4x = 405
9x = 405
x = 405 : 9
x = 45

Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}405\\ \phantom{0}\underset{¯}{36}\\ \phantom{0}\underset{¯}{\phantom{0}}45\\ \phantom{00}\underset{¯}{45}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)9}\\ \overline{\overline{)45}}\end{array}\end{array}$

24x − x = 529
23x = 529
x = 529 : 23
x = 23
Ответ: x = 23

Вычисления:
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}529\\ \phantom{0}\underset{¯}{46}\\ \phantom{0}\underset{¯}{\phantom{0}}69\\ \phantom{00}\underset{¯}{69}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)23}\\ \overline{\overline{)23}}\end{array}\end{array}$