4 Calcula :a) 5 - 7 - 2 - (1 - 9) - 3 + 12] + 4 =b) 1 - ( - 3 + 6 + 1) - [4 - (6 - 3 + 1) - 2) =c) 6 - ( - 9 + 7 - 1) - (3 - ( - 5 + 4 + 6) - 1] =d) 28 - 21 - 12 - 3) - 7) =e) ( - 2 + 3 (2 - 5) 3] - [?
4 Calcula : a) 5 - 7 - 2 - (1 - 9) - 3 + 12] + 4 = b) 1 - ( - 3 + 6 + 1) - [4 - (6 - 3 + 1) - 2) = c) 6 - ( - 9 + 7 - 1) - (3 - ( - 5 + 4 + 6) - 1] = d) 28 - 21 - 12 - 3) - 7) = e) ( - 2 + 3 (2 - 5) 3] - [(3 - 5 + 2) - 2. (3 - 4)] = 1) 8 - 16 - ( - 3 + 7) - 6] + 4 = .