3) -3,25: (-5) + 6,75. [0,78(3) – (+2,3(7)) – (-1,65)].

1. Преобразуем периодические дроби: -3,25 = -13/4, -5 = -5/1, 6,75 = 27/4, 0,78(3) = 78/100 + 3/900 = 702/900 + 3/900 = 705/900 = 47/60.

2. +2,3(7) = 2 + 3/10 + 7/90 = 2 + 27/90 + 7/90 = 2 + 34/90 = 2 + 17/45 = 107/45.

3. -1,65 = -165/100 = -33/20.

4. Подставим и вычислим: 13/20 + 27/4 * [47/60 - 107/45 - (-33/20)] = 13/20 + 27/4 * [47/60 - 107/45 + 33/20] = 13/20 + 27/4 * [(47 - 142.67 + 99)/60] = 13/20 + 27/4 * [0.78333 - 2.37778 + 1.65] = 13/20 + 27/4 * [0.05555] = 0.65 + 6.75 * (1/18) = 0.65 + 0.375 = 1.025.