\[\boxed{\text{60.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[1)\ 300 - (90 + 70) +\]
\[+ (86 - 46) = 300 - 160 +\]
\[+ 40 = 140 + 40 = 180.\]
\[2)\ 90\ :(10 \cdot 9)\ :(9\ :9) =\]
\[= 90\ :90\ :1 = 1.\]
\[3)\ 0 \cdot 8 + 7 = 0 + 7 = 7.\]
\[4)\ 0 \cdot (8 + 7) = 0.\]
\[5)\ 91\ :13 \cdot 7 = 7 \cdot 7 = 49.\]
\[6)\ 84\ :(14 \cdot 3) = 84\ :42 = 2.\ \]