781. a) 5,6 ⋅ 38 – 2,8 ⋅ 56; б) 35 ⋅ 54 + 3,5 ⋅ 460; в) 92 ⋅ 14 + 9,2 ⋅ 60; г) 83 ⋅ 57 + 8,3 ⋅ 430.

a) 5,6 ⋅ 38 – 2,8 ⋅ 56

\[5.6 \cdot 38 - 2.8 \cdot 56 = 212.8 - 156.8 = 56\]

б) 35 ⋅ 54 + 3,5 ⋅ 460

\[35 \cdot 54 + 3.5 \cdot 460 = 1890 + 1610 = 3500\]

в) 92 ⋅ 14 + 9,2 ⋅ 60

\[92 \cdot 14 + 9.2 \cdot 60 = 1288 + 552 = 1840\]

г) 83 ⋅ 57 + 8,3 ⋅ 430

\[83 \cdot 57 + 8.3 \cdot 430 = 4731 + 3569 = 8300\]

Ответ: a) 56; б) 3500; в) 1840; г) 8300