\[\boxed{\text{80.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[1)\ 960\ :3 = (900 + 60)\ :3 =\]
\[= 300 + 20 = 320.\ \]
\[780\ :6 = (600 + 180)\ :6 =\]
\[= 100 + 30 = 130.\ \]
\[945 - 9 \cdot 5\ :3 = 945 - 45\ :3 =\]
\[= 945 - 15 = 930.\]
\[600 + 6 \cdot 7\ :2 = 600 + 42\ :2 =\]
\[= 600 + 21 = 621.\]
\[(200 + 450)\ :5 = 650\ :5 =\]
\[= (500 + 150)\ :5 =\]
\[= 100 + 30 = 130.\]
\[(720 - 120)\ :3 =\]
\[= 600\ :3 = 200.\]
\[2)\ 507 + 230 + 187 = 924\]
\[367 + 178 + 264 = 809\]