39 – 30 + 7; 38 + 1 – 9; 74 – 70 – 4

1. 39 – 30 + 7 = 9 + 7 = 16
2. 38 + 1 – 9 = 39 – 9 = 30
3. 74 – 70 – 4 = 4 – 4 = 0

Ответ:

1. 39 – 30 + 7 = 16
2. 38 + 1 – 9 = 30
3. 74 – 70 – 4 = 0