2. Вычисли. (3+7)+20=30 75-(45-5)=35 80-(10+50)=20 (12-7)+40=45 (30+15)-20=25 (16+74)+6=96

Решение:

1. \( (3 + 7) + 20 = 10 + 20 = 30 \)
2. \( 75 - (45 - 5) = 75 - 40 = 35 \)
3. \( 80 - (10 + 50) = 80 - 60 = 20 \)
4. \( (12 - 7) + 40 = 5 + 40 = 45 \)
5. \( (30 + 15) - 20 = 45 - 20 = 25 \)
6. \( (16 + 74) + 6 = 90 + 6 = 96 \)

Ответ: 30, 35, 20, 45, 25, 96.