5 - 2 = 3 ( cái )
1 + 1 = 2
4
-5.5
1 - 1 = 0
20 - 5 + 6 = 21
20 - 1 + 30 + 10 = 59
1 - 1 + 3 + 4 - 5 = 2
25 - 26 + 17 + 100 = 116
4000 - 5 - 11 = 3984