779. a) 56 ⋅ 13 + 5,6 ⋅ 70; б) 2,7 ⋅ 28 – 1,8 ⋅ 27; в) 3,5 ⋅ 26 – 1,6 ⋅ 35; г) 74 ⋅ 26 + 2,6 ⋅ 260.

a) 56 ⋅ 13 + 5,6 ⋅ 70

\[56 \cdot 13 + 5.6 \cdot 70 = 728 + 392 = 1120\]

б) 2,7 ⋅ 28 – 1,8 ⋅ 27

\[2.7 \cdot 28 - 1.8 \cdot 27 = 75.6 - 48.6 = 27\]

в) 3,5 ⋅ 26 – 1,6 ⋅ 35

\[3.5 \cdot 26 - 1.6 \cdot 35 = 91 - 56 = 35\]

г) 74 ⋅ 26 + 2,6 ⋅ 260

\[74 \cdot 26 + 2.6 \cdot 260 = 1924 + 676 = 2600\]

Ответ: a) 1120; б) 27; в) 35; г) 2600