Условие:

Знаки + и − закрыты карточками. Все равенства верные. Запиши их со знаками действий.
76 _ 20 _ 42 = 54
38 _ 25 _ 12 = 75
68 _ 24 _ 56 = 100
98 _ 75 _ 37 = 60

76 + 20 - 42 = 54
38 + 25 + 12 = 75
68 - 24 + 56 = 100
98 - 75 + 37 = 60
Вычисления:
76 + 20 − 42 = 96 − 42 = 54
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}76\\ 20\end{array}}\\ \begin{array}{r}96\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}96\\ 42\end{array}}\\ \begin{array}{r}54\end{array}\end{array}$
38 + 25 + 12 =63 + 12 = 75
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}38\\ 25\end{array}}\\ \begin{array}{r}63\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}63\\ 12\end{array}}\\ \begin{array}{r}75\end{array}\end{array}$
68 − 24 + 56 = 44 + 56 = 100
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}68\\ 24\end{array}}\\ \begin{array}{r}44\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}44\\ 56\end{array}}\\ \begin{array}{r}100\end{array}\end{array}$
98 − 75 + 37 = 23 + 37 = 60
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}98\\ 75\end{array}}\\ \begin{array}{r}23\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}23\\ 37\end{array}}\\ \begin{array}{r}60\end{array}\end{array}$