1. 60 - 40 = ... 21 + 78 = ... 17 + 38 = ... 50 - 26 = ... 85 - 71 = ... 71 - 67 = ...

Решение:

1. \( 60 - 40 = 20 \)
2. \( 21 + 78 = 99 \)
3. \( 17 + 38 = 55 \)
4. \( 50 - 26 = 24 \)
5. \( 85 - 71 = 14 \)
6. \( 71 - 67 = 4 \)

Ответ: 20, 99, 55, 24, 14, 4.