(324 + 436) − 215 = 760 − 215 = 545

Вычисления:
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}342\\ 436\end{array}}\\ \begin{array}{r}\mathrm{760 }\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}760\\ 215\end{array}}\\ \begin{array}{r}\mathrm{545 }\end{array}\end{array}$

12 * 9 + 515 : 5 = 108 + 103 = 211

Вычисления:
$\begin{array}{r}\times \underset{¯}{\begin{array}{r}12\\ 9\end{array}}\\ 108\end{array}$
 
$\begin{array}{cc}\begin{array}{l}\underset{¯}{\phantom{0}}515\\ \phantom{0}\underset{¯}{5}\\ \phantom{0}\underset{¯}{\phantom{0}}1\\ \phantom{00}\underset{¯}{0}\\ \phantom{0}\underset{¯}{\phantom{0}}15\\ \phantom{00}\underset{¯}{15}\\ \phantom{000}0\end{array}& \begin{array}{l}\overline{)5}\\ \overline{\overline{)103}}\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}108\\ 103\end{array}}\\ \begin{array}{r}\mathrm{211 }\end{array}\end{array}$

(17 + 13) * (17 − 13) = 30 * 4 = 120