Условие:

Вычисли.
(80 − 7) + 13
52 − (6 + 18)
(60 + 8) − 19
40 − (21 − 7)

(80 − 7) + 13 = 86
52 − (6 + 18) = 28
(60 + 8) − 19 = 49
40 − (21 − 7) = 26
Вычисления:
(80 − 7) + 13 = 73 + 13 = 86
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}80\\ 7\end{array}}\\ \begin{array}{r}73\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}73\\ 13\end{array}}\\ \begin{array}{r}86\end{array}\end{array}$
52 − (6 + 18) = 52 − 24 = 28
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}6\\ 18\end{array}}\\ \begin{array}{r}24\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}52\\ 24\end{array}}\\ \begin{array}{r}28\end{array}\end{array}$
(60 + 8) − 19 = 68 − 19 = 49
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}60\\ 8\end{array}}\\ \begin{array}{r}68\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}68\\ 19\end{array}}\\ \begin{array}{r}49\end{array}\end{array}$
40 − (21 − 7) = 40 − 14 = 26
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}21\\ 7\end{array}}\\ \begin{array}{r}14\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}40\\ 14\end{array}}\\ \begin{array}{r}26\end{array}\end{array}$