Ответ:

1. 28 × 189 : 63 - 64 × 18 : 16 = 12

1) 189 × 28 = 5292

2) 5292 : 63 = 84

3) 64 × 18 = 1152

4) 1152 : 16 = 72

5) 84 - 72 = 12

2. (2660 : 76 + 1860 : 124) × 17 - 839 = 11

1) 2660 : 76 = 35

2) 1860 : 124 = 15

3) 35 + 15 = 50

4) 50 × 17 = 850

5) 850 - 839 = 11

3. (1936 : 121 - 14) × (68 ×104 - 7069) = 6

1) 1936 : 121 = 16

2) 16 - 14 = 2

3) 68 × 104 = 7072

4) 7072 - 7069 = 3

5) 2 × 3 = 6