Разберем каждый пример по порядку:
1) \(30 + 20 + 4 = 50 + 4 = 54\)
2) \(80 - 50 + 9 = 30 + 9 = 39\)
3) \(52 - 2 - 20 = 50 - 20 = 30\)
4) \(90 - 40 + 3 = 50 + 3 = 53\)
5) \(60 + 20 + 6 = 80 + 6 = 86\)
6) \(73 - 70 + 80 = 3 + 80 = 83\)
Ответ: 54, 39, 30, 53, 86, 83