Ответ:

Пошаговое объяснение:

1.

1) (3/4 - 4/5) * 7,8 = (15/20 - 16/20) * 7,8 = -1/20 * 7,8 = -0,05 * 7,8 = - 0,39

2) (2/3 + 4/7) * (-7/13) =

(14/21 + 12/21) * (-7/13) =

26/21 * (-7/13) = - 2/3 * 1/1 = -2/3

3) -0,39 - (-2/3) = -39/100 + 2/3 = -117/300 + 200/300 = 83/300

2.

1) (3/7 - 16/21) * (-2 2/7) =

(9/21 - 16/21) * (-16/7) =

-7/21 * (-16/7) = 16/21

2) (11/15 + 0,3) : (-12 2/5) = (11/15 + 3/10) : (-62/5) =

= (22/30 + 9/30) * (-5/62) = 31/30 * (-5/62) = - 1/6 * 1/2 = - 1/12

3) 16/21 + (- 1/12) = 64/84 - 7/84 = 57/84 = 19/28.