\[\boxed{\mathbf{514\ (514)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
Пояснение.
Решение.
\[1)\ (36 \cdot 21)\ :12 =\]
\[= (36\ :12) \cdot 21 = 3 \cdot 21 = 63\]
\[2)\ (40 \cdot 420)\ :60 =\]
\[= 40 \cdot (420\ :60) = 40 \cdot 7 = 280\]
\[3)\ (5 \cdot 6 \cdot 78)\ :3 =\]
\[= 5 \cdot (6\ :3) \cdot 78 = 5 \cdot 2 \cdot 78 =\]
\[= 10 \cdot 78 = 780\]
\[4)\ (45 \cdot 63)\ :81 =\]
\[= (45 \cdot 63)\ :9\ :9 =\]
\[= (45\ :9) \cdot (63\ :9) = 5 \cdot 7 = 35\]
\[\boxed{\ \mathbf{514.}}\]
\(РЕПИН.\)