20:4*8+28:4*7 = 14+12:6*8-45:5 = 18+27:3*8-8 * = 35:5-16:4+9*9=

Первый пример.

20 : 4 * 8 + 28 : 4 * 7 = 89;

20 / 4 = 5;

5 * 8 = 40;

28 / 4 = 7;

7 * 7 = 49;

40 + 49 = 89.

Второй пример.

14 + 12 : 6 * 8 - 45 : 5 = 21;

12 / 6 = 2;

2 * 8 = 16;

45 / 5 = 9;

14 + 16 = 30;

30 - 9 = 21.

Третий пример.

18 + 27 : 3 * 8 - 8 = 82;

27 / 3 = 9;

9 * 8 = 72;

18 + 72 = 90;

90 - 8 = 82.

Четвертый пример.

35 : 5 - 16 : 4 + 9 * 9 = 84;

35 / 5 = 7;

16 / 4 = 4;

9 * 9 = 81;

7 - 4 = 3;

3 + 81 = 84.